diff --git a/lib/Paneset/PaneResizeContainer.js b/lib/Paneset/PaneResizeContainer.js
index e959244af..3efb481fc 100644
--- a/lib/Paneset/PaneResizeContainer.js
+++ b/lib/Paneset/PaneResizeContainer.js
@@ -1,4 +1,4 @@
-import React, { useState, useRef, useEffect, useCallback } from 'react';
+import React, { useState, useRef, useEffect, useCallback, useMemo } from 'react';
 import PropTypes from 'prop-types';
 import cloneDeep from 'lodash/cloneDeep';
 import isEqual from 'lodash/isEqual';
@@ -13,7 +13,7 @@ const PaneResizeContainer = ({ isRoot, children, onElementResize, parentElement,
   const [cursorX, setCursorX] = useState(0);
   const [handles, setHandles] = useState([]);
   const [activeHandle, setActiveHandle] = useState(null);
-  const [update, setUpdate] = useState(0); // eslint-disable-line no-unused-vars
+  const [update, setUpdate] = useState(0);
   const [blocking, setBlocking] = useState(null);
   let container = useRef();
   if (resizeContainerRef) {
@@ -142,9 +142,8 @@ const PaneResizeContainer = ({ isRoot, children, onElementResize, parentElement,
     document.removeEventListener('mousemove', updateCursor);
     document.removeEventListener('mouseup', handleMouseUp);
     document.body.style.userSelect = 'auto';
-    document.body.style.webkitUserSelect = 'auto';
-    document.body.style.msUserSelect = 'auto';
     document.body.style.msUserSelect = 'auto';
+    document.body.style.mozUserSelect = 'auto';
     setDragging(false);
   }, [updateCursor]);
 
@@ -158,7 +157,6 @@ const PaneResizeContainer = ({ isRoot, children, onElementResize, parentElement,
     document.addEventListener('mousemove', updateCursor);
     document.addEventListener('mouseup', handleMouseUp);
     document.body.style.userSelect = 'none';
-    document.body.style.webkitUserSelect = 'none';
     document.body.style.msUserSelect = 'none';
     document.body.style.mozUserSelect = 'none';
   }, [handleMouseUp, handles, updateCursor]);
@@ -184,37 +182,48 @@ const PaneResizeContainer = ({ isRoot, children, onElementResize, parentElement,
     });
   };
 
-  const renderHandles = useCallback(() => {
+  // Reads the DOM (forces layout) to locate each handle. Must only rerun when the handle set,
+  // container/window size, or blocking state changes - never merely because cursorX/dragging/
+  // activeHandle changed during a drag, since handles don't move until the drag ends.
+  const computeHandlePositions = useCallback(() => {
     handleData.current = [];
-    const handleElements = handles.map((h) => {
+    return handles.map((h) => {
       const rect = h.getRef()?.current?.getBoundingClientRect();
-      if (rect) {
-        if (rect.left === 0) {
-          handleData.current.push({ id: h.id, elementId: h.elementId, x: 0, y: 50 });
-          return false;
-        }
+      if (!rect) return null;
 
-        if (!containerRect.current) {
-          containerRect.current = container.current?.getBoundingClientRect();
-        }
-        const newLeft = rect.left - (containerRect.current ? containerRect.current.left : 0);
-        const top = rect.top - (containerRect.current ? containerRect.current.top : 0);
-        handleData.current.push({ id: h.id, elementId: h.elementId, x: newLeft, y: top });
-        return (
-          <PaneResizeHandle
-            key={h.id}
-            id={h.id}
-            xpos={newLeft - 3}
-            active={(activeHandle && h.id === activeHandle.id)}
-            onMouseDown={handleHandleMouseDown}
-          />
-        );
+      if (rect.left === 0) {
+        handleData.current.push({ id: h.id, elementId: h.elementId, x: 0, y: 50 });
+        return { id: h.id, render: false };
+      }
+
+      if (!containerRect.current) {
+        containerRect.current = container.current?.getBoundingClientRect();
       }
-      return null;
+      const newLeft = rect.left - (containerRect.current ? containerRect.current.left : 0);
+      const top = rect.top - (containerRect.current ? containerRect.current.top : 0);
+      handleData.current.push({ id: h.id, elementId: h.elementId, x: newLeft, y: top });
+      return { id: h.id, x: newLeft, render: true };
     });
+  }, [handles]); // eslint-disable-line react-hooks/exhaustive-deps
+
+  const handlePositions = useMemo(
+    () => (blocking ? [] : computeHandlePositions()),
+    [computeHandlePositions, update, blocking]
+  );
 
-    return handleElements;
-  }, [activeHandle, handleHandleMouseDown, handles]);
+  // No DOM reads here, so this is cheap to rerun on every render (mousedown/mousemove/mouseup).
+  const renderHandles = () => handlePositions.map((pos) => {
+    if (!pos || !pos.render) return null;
+    return (
+      <PaneResizeHandle
+        key={pos.id}
+        id={pos.id}
+        xpos={pos.x - 3}
+        active={(activeHandle && pos.id === activeHandle.id)}
+        onMouseDown={handleHandleMouseDown}
+      />
+    );
+  });
 
   // this is the equivalent of `forceUpdate` for functional components.
   const updateHandle = () => {
diff --git a/lib/Paneset/Paneset.js b/lib/Paneset/Paneset.js
index 838dbbd75..330403c2e 100644
--- a/lib/Paneset/Paneset.js
+++ b/lib/Paneset/Paneset.js
@@ -374,33 +374,7 @@ class Paneset extends React.Component {
     ]);
   }
 
-  setStyle = () => {
-    if (this.isThisMounted()) {
-      const {
-        paneset,
-        isRoot
-      } = this.props;
-
-      // for nested, non-root panesets, we resize their element to the edge of the screen.
-      // this resolves a cropping behavior (impetus for STCOM-953) and allows
-      // paneset to accurately resize its children (overflow: hidden)
-      if (paneset && !isRoot) {
-        const containerBounds = this.container.current?.getBoundingClientRect();
-        if (containerBounds.right < window.offsetWidth) {
-          this.setState((curState) => {
-            const {
-              left, right
-            } = containerBounds;
-            const newStyle = { flex: `0 0 ${right - left}px` };
-            return {
-              changeType: 'nested-resize-end',
-              style: { ...curState.style, ...newStyle }
-            };
-          });
-        }
-      }
-    }
-  }
+  setStyle = () => {}
 
   resizePanes = (panes, widths) => {
     if (widths !== null) {