diff --git a/crates/applications/stacked_cores/src/main.rs b/crates/applications/stacked_cores/src/main.rs
index dd511c5..20f9505 100644
--- a/crates/applications/stacked_cores/src/main.rs
+++ b/crates/applications/stacked_cores/src/main.rs
@@ -66,7 +66,7 @@ impl ClockState {
     }
 }
 
-#[derive(Copy, Clone)]
+#[derive(Clone)]
 struct Params {
     input_magnitude: f32,
     clock_phase_duration: f32,
@@ -79,14 +79,19 @@ struct Params {
     // 'io' = drive/control wire
     io_major: f32,
     io_minor: f32,
-    coupling_length: f32,
     coupling_major: f32,
     coupling_minor: f32,
-    coupling_loops: u32,
+    coupling_loops: u32, // per core
     // how far to place S away from the sim edge
     s_xy_buffer: f32,
     // coords for core 'n'
     sz1: f32,
+    couplings: Vec<(
+        u32, /* from core */
+        u32, /* to core */
+        u32, /* shift index */
+        u32, /* coupling group */
+    )>,
 }
 fn um(n: u32) -> f32 {
     n as f32 * 1e-6
@@ -104,9 +109,6 @@ impl Params {
     fn sz(&self, n: u32) -> f32 {
         (n + 1) as f32 * self.sz1
     }
-    fn couplingz(&self, n: u32) -> f32 {
-        0.5 * (self.sz(n) + self.sz(n+1))
-    }
     /// control loop for core n (alternately called "drive" loop)
     fn ctl(&self, n: u32) -> Torus {
         Torus::new_xz(Meters::new(self.sx() - self.s_major, self.sy(), self.sz(n)), self.io_major, self.io_minor)
@@ -118,31 +120,39 @@ impl Params {
     fn s(&self, n: u32) -> Torus {
         Torus::new_xy(Meters::new(self.sx(), self.sy(), self.sz(n)), self.s_major, self.s_minor)
     }
-    fn coupling_angle(&self, set_id: u32, loop_: u32) -> f32 {
-        // coupling onto 2 cores, plus 1 control and an optional sense.
-        let total_loops = self.coupling_loops * 2 + 2;
+    fn coupling_angle(&self, loop_: u32, set_id: u32, of_set: u32) -> f32 {
+        // plus 1 control and an optional sense.
+        let total_loops = self.coupling_loops * of_set + 2;
         // + 1 because we reserve loop 0 for control.
-        let mut idx = loop_ * 2 + 1 + set_id % 2;
+        let mut idx = loop_ * of_set + 1 + set_id;
         // reserve idx = 50% for sense wire.
         if idx >= total_loops / 2 {
             idx += 1;
         }
         idx as f32 / total_loops as f32 * f32::two_pi()
     }
-    /// coupling(n) is the wire which couples core n into core n+1
-    fn coupling(&self, n: u32, loop_: u32) -> Translate<Rotate<ElongatedTorus>> {
-        let angle = self.coupling_angle(n, loop_);
+    /// coupling(n) is the wire which couples core `from` to core `to`.
+    /// - `of_set` indicates how many sets of loops this core has (e.g. 2 if it's coupling separately
+    ///   to the above and below cores, equally).
+    /// - `set_id` is [0, of_set).
+    /// - `loop_` is [0, self.coupling_loops).
+    fn coupling(&self, from: u32, to: u32, loop_: u32, set_id: u32, of_set: u32) -> Translate<Rotate<ElongatedTorus>> {
+        let angle = self.coupling_angle(loop_, set_id, of_set);
+        let from_z = self.sz(from);
+        let to_z = self.sz(to);
+        let center_z = (from_z + to_z) * 0.5;
+        let coupling_length = (to_z - from_z).abs();
         Translate::new(
             Rotate::about_z(
                 angle,
                 ElongatedTorus::new_xz(
                     Meters::new(self.s_major, 0.0, 0.0),
-                    self.coupling_length,
+                    coupling_length,
                     self.coupling_major,
                     self.coupling_minor,
                 ),
             ),
-            Meters::new(self.sx(), self.sy(), self.couplingz(n)),
+            Meters::new(self.sx(), self.sy(), center_z)
         )
     }
 
@@ -166,33 +176,45 @@ impl Params {
             .shifted(start.cast())
     }
 
-    fn with_input_magnitude(mut self, p: f32) -> Self {
-        self.input_magnitude = p;
-        self
+    fn with_input_magnitude(&self, p: f32) -> Self {
+        let mut me = self.clone();
+        me.input_magnitude = p;
+        me
     }
-    fn with_clock_phase_duration(mut self, p: f32) -> Self {
-        self.clock_phase_duration = p;
-        self
+    fn with_clock_phase_duration(&self, p: f32) -> Self {
+        let mut me = self.clone();
+        me.clock_phase_duration = p;
+        me
     }
-    fn with_clock_decay(mut self, p: f32) -> Self {
-        self.clock_decay = p;
-        self
+    fn with_clock_decay(&self, p: f32) -> Self {
+        let mut me = self.clone();
+        me.clock_decay = p;
+        me
     }
-    fn with_ctl_conductivity(mut self, p: f32) -> Self {
-        self.ctl_conductivity = p;
-        self
+    fn with_ctl_conductivity(&self, p: f32) -> Self {
+        let mut me = self.clone();
+        me.ctl_conductivity = p;
+        me
     }
-    fn with_coupling_conductivity(mut self, p: f32) -> Self {
-        self.coupling_conductivity = p;
-        self
+    fn with_coupling_conductivity(&self, p: f32) -> Self {
+        let mut me = self.clone();
+        me.coupling_conductivity = p;
+        me
     }
-    fn with_coupling_loops(mut self, p: u32) -> Self {
-        self.coupling_loops = p;
-        self
+    fn with_coupling_loops(&self, p: u32) -> Self {
+        let mut me = self.clone();
+        me.coupling_loops = p;
+        me
     }
-    fn with_s_major(mut self, p: f32) -> Self {
-        self.s_major = p;
-        self
+    fn with_s_major(&self, p: f32) -> Self {
+        let mut me = self.clone();
+        me.s_major = p;
+        me
+    }
+    fn with_coupling(&self, from: u32, to: u32, id: u32, of: u32) -> Self {
+        let mut me = self.clone();
+        me.couplings.push((from, to, id, of));
+        me
     }
 }
 
@@ -371,393 +393,401 @@ fn main() {
         // 'io' = drive/control wire
         io_major: um(70),
         io_minor: um(20),
-        coupling_length: um(320),
         coupling_major: um(70),
         coupling_minor: um(20),
         coupling_loops: 1,
         s_xy_buffer: um(150),
         // coords for core 'n'
         sz1: um(320),
+        couplings: Vec::new(),
     };
-    // TODO: use a deque, with push_front and push_back
-    let deferred = || {}; // add to this to schedule sims at a lower priority
+    // if false {
+    //     let p17x = params
+    //         .with_clock_phase_duration(ps(2000))
+    //         .with_clock_decay(ps(100))
+    //         .with_input_magnitude(5e9)
+    //         .with_ctl_conductivity(1e3)
+    //         .with_coupling_conductivity(1e4)
+    //         .with_s_major(um(160))
+    //     ;
+    //     run_sim(
+    //         "171-2ns-100ps-5e9A-1e3pctl-1e4pcpl-4loops",
+    //         drive_map_isolated_inv(),
+    //         p17x.with_coupling_loops(4),
+    //     );
+    //     run_sim(
+    //         "172-2ns-100ps-5e9A-1e3pctl-1e4pcpl-2loops",
+    //         drive_map_isolated_inv(),
+    //         p17x.with_coupling_loops(2),
+    //     );
+    //     run_sim(
+    //         "173-2ns-100ps-5e9A-1e3pctl-1e4pcpl-1loops",
+    //         drive_map_isolated_inv(),
+    //         p17x.with_coupling_loops(1),
+    //     );
+    //     run_sim(
+    //         "174-2ns-100ps-5e9A-1e3pctl-1e4pcpl-6loops",
+    //         drive_map_isolated_inv(),
+    //         p17x.with_coupling_loops(6),
+    //     );
+    // }
+    // if false {
+    //     let p3xx = params
+    //         .with_clock_phase_duration(ps(2000))
+    //         .with_clock_decay(ps(100))
+    //         .with_input_magnitude(5e10)
+    //         .with_ctl_conductivity(1e3)
+    //         .with_coupling_conductivity(1e4)
+    //         .with_s_major(um(400))
+    //     ;
+    //     run_sim(
+    //         "301-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-1loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(1),
+    //     );
+    //     run_sim(
+    //         "302-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-2loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(2),
+    //     );
+    //     run_sim(
+    //         "304-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-4loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(4),
+    //     );
+    //     run_sim(
+    //         "308-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-8loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(8),
+    //     );
+    //     run_sim(
+    //         "312-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-12loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(12),
+    //     );
+    //     run_sim(
+    //         "316-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-16loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(16),
+    //     );
+    //     run_sim(
+    //         "320-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-20loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(20),
+    //     );
+    //     run_sim(
+    //         "324-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-24loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(24),
+    //     );
+    //     run_sim(
+    //         "328-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-28loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(28),
+    //     );
+    //     run_sim(
+    //         "332-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-32loops",
+    //         drive_map_isolated_inv(),
+    //         p3xx.with_coupling_loops(32),
+    //     );
+    // }
+    // if false {
+    //     let p4xx = params
+    //         .with_clock_phase_duration(ps(1000))
+    //         .with_clock_decay(ps(50))
+    //         .with_input_magnitude(8e10)
+    //         .with_ctl_conductivity(5e2)
+    //         .with_coupling_conductivity(5e3)
+    //         .with_s_major(um(400))
+    //         .with_coupling(1, 0, 0, 2)
+    //         .with_coupling(1, 2, 1, 2)
+    //     ;
+    //     run_sim(
+    //         "401-1loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(1),
+    //     );
+    //     run_sim(
+    //         "402-2loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(2),
+    //     );
+    //     run_sim(
+    //         "404-4loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(4),
+    //     );
+    //     run_sim(
+    //         "406-6loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(6),
+    //     );
+    //     run_sim(
+    //         "408-8loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(8),
+    //     );
+    //     run_sim(
+    //         "410-10loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(10),
+    //     );
+    //     run_sim(
+    //         "412-12loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(12),
+    //     );
+    //     run_sim(
+    //         "416-16loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(16),
+    //     );
+    //     run_sim(
+    //         "420-20loops",
+    //         drive_map_3stack(),
+    //         p4xx.with_coupling_loops(20),
+    //     );
+    // }
+    // if false {
+    //     let p5xx = params
+    //         .with_clock_phase_duration(ps(1000))
+    //         .with_clock_decay(ps(50))
+    //         .with_input_magnitude(8e10)
+    //         .with_ctl_conductivity(5e2)
+    //         .with_coupling_conductivity(5e3)
+    //         .with_s_major(um(400))
+    //         .with_coupling(0, 1, 0, 2)
+    //         .with_coupling(1, 2, 1, 2)
+    //     ;
+    //     run_sim(
+    //         "501-1loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(1),
+    //     );
+    //     run_sim(
+    //         "502-2loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(2),
+    //     );
+    //     run_sim(
+    //         "504-4loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(4),
+    //     );
+    //     run_sim(
+    //         "506-6loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(6),
+    //     );
+    //     run_sim(
+    //         "508-8loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(8),
+    //     );
+    //     run_sim(
+    //         "510-10loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(10),
+    //     );
+    //     run_sim(
+    //         "512-12loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(12),
+    //     );
+    //     run_sim(
+    //         "516-16loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(16),
+    //     );
+    //     run_sim(
+    //         "520-20loops",
+    //         drive_map_3stack_one_sided(),
+    //         p5xx.with_coupling_loops(20),
+    //     );
+    // }
+    // if false {
+    //     let p6xx = params
+    //         .with_clock_phase_duration(ps(1000))
+    //         .with_clock_decay(ps(50))
+    //         .with_input_magnitude(8e10)
+    //         .with_ctl_conductivity(5e2)
+    //         .with_coupling_conductivity(5e3)
+    //         .with_s_major(um(400))
+    //         .with_coupling(0, 1, 0, 2)
+    //         .with_coupling(1, 2, 1, 2)
+    //     ;
+    //     run_sim(
+    //         "601-1loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(1),
+    //     );
+    //     run_sim(
+    //         "602-2loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(2),
+    //     );
+    //     run_sim(
+    //         "604-4loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(4),
+    //     );
+    //     run_sim(
+    //         "606-6loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(6),
+    //     );
+    //     run_sim(
+    //         "608-8loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(8),
+    //     );
+    //     run_sim(
+    //         "610-10loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(10),
+    //     );
+    //     run_sim(
+    //         "612-12loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(12),
+    //     );
+    //     run_sim(
+    //         "616-16loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(16),
+    //     );
+    //     run_sim(
+    //         "620-20loops",
+    //         drive_map_3stack_one_sided_inv(),
+    //         p6xx.with_coupling_loops(20),
+    //     );
+    // }
+    // if false {
+    //     let p7xx = params
+    //         .with_clock_phase_duration(ps(1000))
+    //         .with_clock_decay(ps(50))
+    //         .with_input_magnitude(8e10)
+    //         .with_ctl_conductivity(5e2)
+    //         .with_coupling_conductivity(5e3)
+    //         .with_s_major(um(400))
+    //         .with_coupling(0, 1, 0, 2)
+    //         .with_coupling(1, 2, 1, 2)
+    //         .with_coupling(2, 3, 0, 2)
+    //         .with_coupling(3, 4, 1, 2)
+    //     ;
+    //     run_sim(
+    //         "701-1loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(1),
+    //     );
+    //     run_sim(
+    //         "702-2loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(2),
+    //     );
+    //     run_sim(
+    //         "704-4loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(4),
+    //     );
+    //     run_sim(
+    //         "706-6loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(6),
+    //     );
+    //     run_sim(
+    //         "708-8loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(8),
+    //     );
+    //     run_sim(
+    //         "710-10loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(10),
+    //     );
+    //     run_sim(
+    //         "712-12loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(12),
+    //     );
+    //     run_sim(
+    //         "716-16loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(16),
+    //     );
+    //     run_sim(
+    //         "720-20loops",
+    //         drive_map_5stack_one_sided_inv(),
+    //         p7xx.with_coupling_loops(20),
+    //     );
+    // }
+    // if false {
+    //     let p8xx = params
+    //         .with_clock_phase_duration(ps(1000))
+    //         .with_clock_decay(ps(50))
+    //         .with_input_magnitude(8e10)
+    //         .with_ctl_conductivity(5e2)
+    //         .with_coupling_conductivity(5e3)
+    //         .with_s_major(um(400))
+    //         .with_coupling_loops(16)
+    //     ;
+    //     run_sim(
+    //         "803-3core",
+    //         drive_map_nstack_one_sided_inv::<3>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "805-5core",
+    //         drive_map_nstack_one_sided_inv::<5>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "807-7core",
+    //         drive_map_nstack_one_sided_inv::<7>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "809-9core",
+    //         drive_map_nstack_one_sided_inv::<9>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "811-11core",
+    //         drive_map_nstack_one_sided_inv::<11>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "813-13core",
+    //         drive_map_nstack_one_sided_inv::<13>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "815-15core",
+    //         drive_map_nstack_one_sided_inv::<15>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "817-17core",
+    //         drive_map_nstack_one_sided_inv::<17>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "819-19core",
+    //         drive_map_nstack_one_sided_inv::<19>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "820-20core",
+    //         drive_map_nstack_one_sided_inv::<20>(),
+    //         p8xx,
+    //     );
+    //     run_sim(
+    //         "821-21core",
+    //         drive_map_nstack_one_sided_inv::<21>(),
+    //         p8xx,
+    //     );
+    // }
     if false {
-        let p17x = params
-            .with_clock_phase_duration(ps(2000))
-            .with_clock_decay(ps(100))
-            .with_input_magnitude(5e9)
-            .with_ctl_conductivity(1e3)
-            .with_coupling_conductivity(1e4)
-            .with_s_major(um(160))
-        ;
-        run_sim(
-            "171-2ns-100ps-5e9A-1e3pctl-1e4pcpl-4loops",
-            drive_map_isolated_inv(),
-            p17x.with_coupling_loops(4),
-        );
-        run_sim(
-            "172-2ns-100ps-5e9A-1e3pctl-1e4pcpl-2loops",
-            drive_map_isolated_inv(),
-            p17x.with_coupling_loops(2),
-        );
-        run_sim(
-            "173-2ns-100ps-5e9A-1e3pctl-1e4pcpl-1loops",
-            drive_map_isolated_inv(),
-            p17x.with_coupling_loops(1),
-        );
-        run_sim(
-            "174-2ns-100ps-5e9A-1e3pctl-1e4pcpl-6loops",
-            drive_map_isolated_inv(),
-            p17x.with_coupling_loops(6),
-        );
-    }
-    if false {
-        let p3xx = params
-            .with_clock_phase_duration(ps(2000))
-            .with_clock_decay(ps(100))
-            .with_input_magnitude(5e10)
-            .with_ctl_conductivity(1e3)
-            .with_coupling_conductivity(1e4)
-            .with_s_major(um(400))
-        ;
-        run_sim(
-            "301-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-1loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(1),
-        );
-        run_sim(
-            "302-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-2loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(2),
-        );
-        run_sim(
-            "304-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-4loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(4),
-        );
-        run_sim(
-            "308-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-8loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(8),
-        );
-        run_sim(
-            "312-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-12loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(12),
-        );
-        run_sim(
-            "316-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-16loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(16),
-        );
-        run_sim(
-            "320-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-20loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(20),
-        );
-        run_sim(
-            "324-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-24loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(24),
-        );
-        run_sim(
-            "328-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-28loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(28),
-        );
-        run_sim(
-            "332-2ns-100ps-5e10A-1e3pctl-1e4pcpl-400um-32loops",
-            drive_map_isolated_inv(),
-            p3xx.with_coupling_loops(32),
-        );
-    }
-    if false {
-        let p4xx = params
-            .with_clock_phase_duration(ps(1000))
-            .with_clock_decay(ps(50))
-            .with_input_magnitude(8e10)
-            .with_ctl_conductivity(5e2)
-            .with_coupling_conductivity(5e3)
-            .with_s_major(um(400))
-        ;
-        run_sim(
-            "401-1loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(1),
-        );
-        run_sim(
-            "402-2loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(2),
-        );
-        run_sim(
-            "404-4loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(4),
-        );
-        run_sim(
-            "406-6loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(6),
-        );
-        run_sim(
-            "408-8loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(8),
-        );
-        run_sim(
-            "410-10loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(10),
-        );
-        run_sim(
-            "412-12loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(12),
-        );
-        run_sim(
-            "416-16loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(16),
-        );
-        run_sim(
-            "420-20loops",
-            drive_map_3stack(),
-            p4xx.with_coupling_loops(20),
-        );
-    }
-    if false {
-        let p5xx = params
-            .with_clock_phase_duration(ps(1000))
-            .with_clock_decay(ps(50))
-            .with_input_magnitude(8e10)
-            .with_ctl_conductivity(5e2)
-            .with_coupling_conductivity(5e3)
-            .with_s_major(um(400))
-        ;
-        run_sim(
-            "501-1loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(1),
-        );
-        run_sim(
-            "502-2loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(2),
-        );
-        run_sim(
-            "504-4loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(4),
-        );
-        run_sim(
-            "506-6loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(6),
-        );
-        run_sim(
-            "508-8loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(8),
-        );
-        run_sim(
-            "510-10loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(10),
-        );
-        run_sim(
-            "512-12loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(12),
-        );
-        run_sim(
-            "516-16loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(16),
-        );
-        run_sim(
-            "520-20loops",
-            drive_map_3stack_one_sided(),
-            p5xx.with_coupling_loops(20),
-        );
-    }
-    if false {
-        let p6xx = params
-            .with_clock_phase_duration(ps(1000))
-            .with_clock_decay(ps(50))
-            .with_input_magnitude(8e10)
-            .with_ctl_conductivity(5e2)
-            .with_coupling_conductivity(5e3)
-            .with_s_major(um(400))
-        ;
-        run_sim(
-            "601-1loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(1),
-        );
-        run_sim(
-            "602-2loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(2),
-        );
-        run_sim(
-            "604-4loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(4),
-        );
-        run_sim(
-            "606-6loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(6),
-        );
-        run_sim(
-            "608-8loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(8),
-        );
-        run_sim(
-            "610-10loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(10),
-        );
-        run_sim(
-            "612-12loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(12),
-        );
-        run_sim(
-            "616-16loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(16),
-        );
-        run_sim(
-            "620-20loops",
-            drive_map_3stack_one_sided_inv(),
-            p6xx.with_coupling_loops(20),
-        );
-    }
-    if false {
-        let p7xx = params
-            .with_clock_phase_duration(ps(1000))
-            .with_clock_decay(ps(50))
-            .with_input_magnitude(8e10)
-            .with_ctl_conductivity(5e2)
-            .with_coupling_conductivity(5e3)
-            .with_s_major(um(400))
-        ;
-        run_sim(
-            "701-1loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(1),
-        );
-        run_sim(
-            "702-2loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(2),
-        );
-        run_sim(
-            "704-4loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(4),
-        );
-        run_sim(
-            "706-6loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(6),
-        );
-        run_sim(
-            "708-8loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(8),
-        );
-        run_sim(
-            "710-10loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(10),
-        );
-        run_sim(
-            "712-12loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(12),
-        );
-        run_sim(
-            "716-16loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(16),
-        );
-        run_sim(
-            "720-20loops",
-            drive_map_5stack_one_sided_inv(),
-            p7xx.with_coupling_loops(20),
-        );
-    }
-    if false {
-        let p8xx = params
-            .with_clock_phase_duration(ps(1000))
-            .with_clock_decay(ps(50))
-            .with_input_magnitude(8e10)
-            .with_ctl_conductivity(5e2)
-            .with_coupling_conductivity(5e3)
-            .with_s_major(um(400))
-            .with_coupling_loops(16)
-        ;
-        run_sim(
-            "803-3core",
-            drive_map_nstack_one_sided_inv::<3>(),
-            p8xx,
-        );
-        run_sim(
-            "805-5core",
-            drive_map_nstack_one_sided_inv::<5>(),
-            p8xx,
-        );
-        run_sim(
-            "807-7core",
-            drive_map_nstack_one_sided_inv::<7>(),
-            p8xx,
-        );
-        run_sim(
-            "809-9core",
-            drive_map_nstack_one_sided_inv::<9>(),
-            p8xx,
-        );
-        run_sim(
-            "811-11core",
-            drive_map_nstack_one_sided_inv::<11>(),
-            p8xx,
-        );
-        run_sim(
-            "813-13core",
-            drive_map_nstack_one_sided_inv::<13>(),
-            p8xx,
-        );
-        run_sim(
-            "815-15core",
-            drive_map_nstack_one_sided_inv::<15>(),
-            p8xx,
-        );
-        run_sim(
-            "817-17core",
-            drive_map_nstack_one_sided_inv::<17>(),
-            p8xx,
-        );
-        run_sim(
-            "819-19core",
-            drive_map_nstack_one_sided_inv::<19>(),
-            p8xx,
-        );
-        run_sim(
-            "820-20core",
-            drive_map_nstack_one_sided_inv::<20>(),
-            p8xx,
-        );
-        run_sim(
-            "821-21core",
-            drive_map_nstack_one_sided_inv::<21>(),
-            p8xx,
-        );
-    }
-    if true {
         let p9xx = params
             .with_clock_phase_duration(ps(1000))
             .with_clock_decay(ps(50))
@@ -765,6 +795,8 @@ fn main() {
             .with_ctl_conductivity(5e2)
             .with_coupling_conductivity(5e3)
             .with_s_major(um(400))
+            .with_coupling(1, 0, 0, 2)
+            .with_coupling(1, 2, 1, 2)
         ;
         run_sim(
             "912-12loops",
@@ -812,41 +844,64 @@ fn main() {
             p9xx.with_coupling_loops(4),
         );
     }
-    // run_sim(
-    //     "76-2ns-100ps-1e10A-1e3pctl-1e4pcpl-4loops",
-    //     drive_map_isolated_inv(),
-    //     params
-    //         .with_clock_phase_duration(ps(2000))
-    //         .with_clock_decay(ps(100))
-    //         .with_input_magnitude(1e10)
-    //         .with_ctl_conductivity(1e3)
-    //         .with_coupling_conductivity(1e4)
-    //         .with_coupling_loops(4)
-    // );
-    // run_sim(
-    //     "82-2ns-100ps-5e10A-1e3pctl-1e4pcpl-4loops",
-    //     drive_map_isolated_inv(),
-    //     params
-    //         .with_clock_phase_duration(ps(2000))
-    //         .with_clock_decay(ps(100))
-    //         .with_input_magnitude(5e10)
-    //         .with_ctl_conductivity(1e3)
-    //         .with_coupling_conductivity(1e4)
-    //         .with_coupling_loops(4)
-    // );
-    // run_sim(
-    //     "85-2ns-100ps-1e11A-1e2pctl-1e4pcpl-4loops",
-    //     drive_map_isolated_inv(),
-    //     params
-    //         .with_clock_phase_duration(ps(2000))
-    //         .with_clock_decay(ps(100))
-    //         .with_input_magnitude(1e11)
-    //         .with_ctl_conductivity(1e2)
-    //         .with_coupling_conductivity(1e4)
-    //         .with_coupling_loops(4)
-    // );
-
-    deferred();
+    if true {
+        let p10xx = params
+            .with_clock_phase_duration(ps(1000))
+            .with_clock_decay(ps(50))
+            .with_input_magnitude(8e10)
+            .with_ctl_conductivity(5e2)
+            .with_coupling_conductivity(5e3)
+            .with_s_major(um(400))
+            .with_coupling(1, 0, 0, 3)
+            .with_coupling(1, 2, 1, 3)
+            .with_coupling(0, 2, 2, 3)
+        ;
+        run_sim(
+            "1008-8loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(8),
+        );
+        run_sim(
+            "1010-10loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(10),
+        );
+        run_sim(
+            "1012-12loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(12),
+        );
+        run_sim(
+            "1006-6loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(6),
+        );
+        run_sim(
+            "1014-14loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(14),
+        );
+        run_sim(
+            "1001-1loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(1),
+        );
+        run_sim(
+            "1002-2loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(2),
+        );
+        run_sim(
+            "1004-4loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(4),
+        );
+        run_sim(
+            "1016-16loops",
+            drive_map_3stack_and_rev(),
+            p10xx.with_coupling_loops(16),
+        );
+    }
 }
 
 
@@ -890,7 +945,7 @@ fn run_sim<const C: usize, const R: usize>(
     let coupling_mat = IsomorphicConductor::new(params.coupling_conductivity.cast::<R>());
     let ferro_mat = Ferroxcube3R1MH::new();
 
-    let last_core = num_cores - 1;
+    // let last_core = num_cores - 1;
 
     let mut driver = Driver::new(Sim::new(
         sim_bounds(num_cores).to_index(feat_size), feat_size,
@@ -902,9 +957,9 @@ fn run_sim<const C: usize, const R: usize>(
     for core in 0..num_cores {
         driver.fill_region(&params.s(core), ferro_mat);
         driver.fill_region(&params.ctl(core), ctl_mat);
-        if core != last_core {
+        for &(from, to, id, of) in &params.couplings {
             for loop_ in 0..params.coupling_loops {
-                driver.fill_region(&params.coupling(core, loop_), coupling_mat);
+                driver.fill_region(&params.coupling(from, to, loop_, id, of), coupling_mat);
             }
         }
     }
@@ -916,17 +971,12 @@ fn run_sim<const C: usize, const R: usize>(
             params.ctl(core),
         ));
     }
-    for core in 0..num_cores {
-        let name = format!("sense{}", core);
-        if core != last_core {
-            driver.add_measurement(meas::CurrentLoop::new(
-                &name, params.coupling(core, 0),
-            ));
-        } else {
-            // driver.add_measurement(meas::CurrentLoop::new(
-            //     &name, params.sense(core),
-            // ));
-        }
+    for &(from, to, id, of) in &params.couplings {
+        let name = format!("sense{}_{}", from, to);
+        // measure just *one* of the coupling loops
+        driver.add_measurement(meas::CurrentLoop::new(
+            &name, params.coupling(from, to, 0, id, of),
+        ));
     }
     for core in 0..num_cores {
         driver.add_measurement(meas::MagneticLoop::new(
@@ -947,7 +997,7 @@ fn run_sim<const C: usize, const R: usize>(
     let prefix = format!("out/applications/stacked_cores/{}/", name);
     let _ = std::fs::create_dir_all(&prefix);
     driver.add_state_file(&*format!("{}state.bc", prefix), 25600);
-    // driver.add_serializer_renderer(&*format!("{}frame-", prefix), 6400, Some(12800));
+    driver.add_serializer_renderer(&*format!("{}frame-", prefix), 6400, Some(12800));
     // driver.add_csv_renderer(&*format!("{}meas-detailed.csv", prefix), 100, None);
     driver.add_csv_renderer(&*format!("{}meas.csv", prefix), 1600, None);
     driver.add_csv_renderer(&*format!("{}meas-sparse.csv", prefix), 12800, None);