diff --git a/src/geo/polygons.js b/src/geo/polygons.js
index 5d4e17a1..5d8304e1 100644
--- a/src/geo/polygons.js
+++ b/src/geo/polygons.js
@@ -288,15 +288,7 @@
      * @returns {Polygon[]} out
      */
     function subtract(setA, setB, outA, outB, z, minArea) {
-        let clib = self.ClipperLib,
-            ctyp = clib.ClipType,
-            ptyp = clib.PolyType,
-            cfil = clib.PolyFillType,
-            clip = new clib.Clipper(),
-            ctre = new clib.PolyTree(),
-            sp1 = toClipper(setA),
-            sp2 = toClipper(setB),
-            min = minArea || 0.1,
+        let min = minArea || 0.1,
             out = [];
 
         function filter(from, to = []) {
@@ -309,10 +301,17 @@
             return to;
         }
 
-        const JS = true;
+        if (true) {
+            let clib = self.ClipperLib,
+                ctyp = clib.ClipType,
+                ptyp = clib.PolyType,
+                cfil = clib.PolyFillType,
+                clip = new clib.Clipper(),
+                ctre = new clib.PolyTree(),
+                sp1 = toClipper(setA),
+                sp2 = toClipper(setB);
 
-        if (JS) {
-            // expensive but worth it?
+            // more expensive? worth it?
             clip.StrictlySimple = true;
             if (outA) {
                 clip.AddPaths(sp1, ptyp.ptSubject, true);
diff --git a/src/mode/fdm/slice.js b/src/mode/fdm/slice.js
index cbee0860..b35a8f41 100644
--- a/src/mode/fdm/slice.js
+++ b/src/mode/fdm/slice.js
@@ -451,6 +451,7 @@
                     projectFlats(slice, solidLayers);
                     projectBridges(slice, solidLayers);
                 }, "layer deltas");
+                // console.log('start'); await BASE.util.ptimer(1000);
                 let promises = doConcurrent ? [] : undefined;
                 forSlices(0.35, promises ? 0.4 : 0.5, slice => {
                     let params = slice.params || spro;
@@ -466,6 +467,7 @@
                         trackupdate(i / t, 0.4, 0.5);
                     });
                 }
+                // console.log('stop'); await BASE.util.ptimer(1000);
             }
 
             // sparse layers only present when non-vase mose and sparse % > 0
@@ -1164,7 +1166,6 @@
             gap = proc.sliceSupportGap,
             min = minArea || 0.01,
             size = (pillarSize || 1),
-            mergeDist = size * 3, // pillar merge dist
             tops = slice.topPolys(),
             trimTo = tops;
 
@@ -1181,6 +1182,15 @@
             down_tops = down ? down.topPolys() : null,
             down_traces = down ? POLY.flatten(down.topShells().clone(true)) : null;
 
+        if (down_tops) {
+            // de-rez complex polys because it's not that important for supports
+            let points = down_tops.map(p => p.deepLength).reduce((a,v)=>a+v);
+            if (points > 200) {
+                down_tops = down_tops.map(p => p.clean(true, undefined, CONF.clipper / 10));
+                down_traces = down_traces.map(p => p.clean(true, undefined, CONF.clipper / 10));
+            }
+        }
+
         // check if point is supported by layer below
         function checkPointSupport(point) {
             // skip points close to other support points