diff --git a/src/kiri/init.js b/src/kiri/init.js
index 013f2992..8e8ff20a 100644
--- a/src/kiri/init.js
+++ b/src/kiri/init.js
@@ -198,7 +198,7 @@
         // }
         API.conf.update();
         DOC.activeElement.blur();
-        // API.event.emit("boolean.click");
+        API.event.emit("boolean.click");
     }
 
     function onButtonClick(ev) {
@@ -1691,7 +1691,7 @@
 
             sliceSupportGen:     UC.newRow([
                 UI.ssaGen = UC.newButton(LANG.sp_detect, onButtonClick, {class: "f-col grow a-center"})
-            ], { modes: FDM, class: "ext-buttons f-row grow", xshow:isNotBelt }),
+            ], { modes: FDM, class: "ext-buttons f-row grow" }),
             fdmSep:              UC.newBlank({class:"pop-sep", modes:FDM, show:isNotBelt}),
             sliceSupportManual: UC.newRow([
                 (UI.ssmAdd = UC.newButton(undefined, onButtonClick, {icon:'<i class="fas fa-plus"></i>'})),
diff --git a/src/kiri/print.js b/src/kiri/print.js
index a7545ce9..eb4f6467 100644
--- a/src/kiri/print.js
+++ b/src/kiri/print.js
@@ -564,7 +564,9 @@
         }
 
         function intersectsTop(p1, p2) {
-            return retractRequired(p1, p2);
+            if (opt.danger) {
+                return retractRequired(p1, p2);
+            }
             let int = false;
             POLY.flatten(slice.topPolys().clone(true)).forEach(function(poly) {
                 if (!int) poly.forEachSegment(function(s1, s2) {
diff --git a/src/mode/fdm/client.js b/src/mode/fdm/client.js
index 046dee70..5cced634 100644
--- a/src/mode/fdm/client.js
+++ b/src/mode/fdm/client.js
@@ -102,6 +102,23 @@
               }
         }
 
+        api.event.on("boolean.click", func.updateSupportButtons = () => {
+            if (!isFdmMode) {
+                return;
+            }
+            for (let btn of [
+                UI.ssaGen,
+                UI.ssmAdd,
+                UI.ssmDun,
+                UI.ssmClr
+            ]) {
+                btn.disabled = UI.sliceSupportEnable.checked;
+            }
+            if (UI.sliceSupportEnable.checked) {
+                func.sclear();
+            }
+        });
+
         api.event.on("function.animate", (mode) => {
             if (!isFdmMode) {
                 return;
@@ -160,6 +177,7 @@
         });
         api.event.on("settings.saved", (settings) => {
             updateRanges(settings.process.ranges);
+            func.updateSupportButtons();
             // let ranges = settings.process.ranges;
             // UI.rangeGroup.style.display = isFdmMode && ranges && ranges.length ? 'flex' : 'none';
         });
@@ -217,8 +235,9 @@
         });
         api.event.on("fdm.supports.clear", func.sclear = () => {
             func.sdone();
-            clearAllWidgetSupports();
-            API.conf.save();
+            if (clearAllWidgetSupports()) {
+                API.conf.save();
+            }
         });
         api.event.on("slice.begin", () => {
             if (!isFdmMode) {
@@ -495,18 +514,23 @@
     }
 
     function clearAllWidgetSupports() {
+        let cleared = 0;
         API.widgets.all().forEach(widget => {
-            clearWidgetSupports(widget);
+            cleared += clearWidgetSupports(widget);
         });
+        return cleared;
     }
 
     function clearWidgetSupports(widget) {
+        let cleared = 0;
         Object.values(widget.sups || {}).forEach(support => {
             widget.adds.remove(support.box);
             widget.mesh.remove(support.box);
+            cleared++;
         });
         widget.sups = {};
         delete API.widgets.annotate(widget.id).support;
+        return cleared;
     }
 
     function delbox(name) {
diff --git a/src/mode/fdm/prepare.js b/src/mode/fdm/prepare.js
index e2bae31c..c6448d25 100644
--- a/src/mode/fdm/prepare.js
+++ b/src/mode/fdm/prepare.js
@@ -32,6 +32,7 @@
             isBelt = device.bedBelt,
             isThin = controller.lineType === "line",
             isFlat = controller.lineType === "flat",
+            isDanger = controller.danger || false,
             firstLayerHeight = isBelt ? process.sliceHeight : process.firstSliceHeight || process.sliceHeight,
             firstLayerSeek = process.outputSeekrate,
             firstLayerRate = process.firstLayerRate,
@@ -84,7 +85,8 @@
                 });
                 // nest and offset tops
                 POLY.nest(tops).forEach(function(poly) {
-                    poly.offset(-offset + nozzle / 2).forEach(function(brim) {
+                    let off = poly.offset(-offset + nozzle / 2);
+                    if (off) off.forEach(function(brim) {
                         brim.move(widget.track.pos);
                         brims.push(brim);
                     });
@@ -92,7 +94,7 @@
             });
 
             // merge brims
-            brims = POLY.union(brims);
+            brims = POLY.union(brims, undefined, true);
 
             // if brim is offset, over-expand then shrink to induce brims to merge
             if (offset && brims.length) {
@@ -412,6 +414,7 @@
                     layerout,
                     {
                         seedPoint: printPoint.sub(offset),
+                        danger: isDanger,
                         params, // range parameters
                         first: slice.index === 0,
                         support: slice.widget.support,