diff --git a/E03_StabSection/E03_StabSection_Router_WhatIf.py b/E03_StabSection/E03_StabSection_Router_WhatIf.py
index 6eb721d60..9380dda50 100644
--- a/E03_StabSection/E03_StabSection_Router_WhatIf.py
+++ b/E03_StabSection/E03_StabSection_Router_WhatIf.py
@@ -260,6 +260,8 @@ def run_whatif(root: Path, station_key: str, req: WhatIfRequest) -> dict[str, An
                 start,
                 max_ratio=SUPPORT_MAX_LEN,
                 step=SUPPORT_LEN_STEP,
+                # 길이 대 Fs 가 늘 단조롭지 않음(활동면이 깊어짐) — 1 m 성긴 걸음 뒤 이분
+                coarse=max(1, round(SUPPORT_MAX_LEN - start)),
             )
         else:
             found = {"found": None, "tried": []}
diff --git a/E03_StabSection/E03_StabSection_UI_Reinforce.ts b/E03_StabSection/E03_StabSection_UI_Reinforce.ts
index de3893053..58216e0d5 100644
--- a/E03_StabSection/E03_StabSection_UI_Reinforce.ts
+++ b/E03_StabSection/E03_StabSection_UI_Reinforce.ts
@@ -278,7 +278,7 @@ export function buildReinforce(o: ReinforceOptions): HTMLElement {
       toggles: { map: false, centers: false, candidates: false },
       picked: null,
     };
-    requestAnimationFrame(() => canvas.render(draw));
+    canvas.render(draw); // 붙기 전 = 기본 폭 · 붙으면 ResizeObserver 가 다시 그림
   }
   if (o.row.walls) {
     const method = createSelectField({
diff --git a/E03_StabSection/E03_StabSection_UI_Section.ts b/E03_StabSection/E03_StabSection_UI_Section.ts
index 391467554..ff43d86e6 100644
--- a/E03_StabSection/E03_StabSection_UI_Section.ts
+++ b/E03_StabSection/E03_StabSection_UI_Section.ts
@@ -346,10 +346,10 @@ export function createSectionCanvas(onPick: (index: number | null) => void): Sec
           ...ns,
         }),
         svgEl("rect", {
-          x: s.head[0] - 2.5 * unit,
-          y: s.head[1] - 2.5 * unit,
-          width: 5 * unit,
-          height: 5 * unit,
+          x: s.head[0] - 1.2 * unit,
+          y: s.head[1] - 1.2 * unit,
+          width: 2.4 * unit,
+          height: 2.4 * unit,
           class: "e03-support__head",
         }),
       );
@@ -358,7 +358,7 @@ export function createSectionCanvas(onPick: (index: number | null) => void): Sec
           svgEl("circle", {
             cx: s.cross[0],
             cy: s.cross[1],
-            r: 3 * unit,
+            r: 1.5 * unit,
             class: "e03-support__cross",
             "data-role": "support-cross",
             ...ns,
diff --git a/E03_StabSection/E03_StabSection_UI_Support.css b/E03_StabSection/E03_StabSection_UI_Support.css
index c2d8207ed..bc2f77b62 100644
--- a/E03_StabSection/E03_StabSection_UI_Support.css
+++ b/E03_StabSection/E03_StabSection_UI_Support.css
@@ -53,3 +53,10 @@
   vertical-align: middle;
   background: var(--e03-support);
 }
+
+.e03-support-fields {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(96px, 1fr));
+  gap: var(--spacing-8);
+  align-items: end;
+}
diff --git a/E03_StabSection/E03_StabSection_UI_Support.ts b/E03_StabSection/E03_StabSection_UI_Support.ts
index 7d87b6cfa..07c8f829b 100644
--- a/E03_StabSection/E03_StabSection_UI_Support.ts
+++ b/E03_StabSection/E03_StabSection_UI_Support.ts
@@ -182,7 +182,7 @@ export function buildSupport(o: SupportOptions): HTMLElement {
   });
   typeField.select.dataset.role = "support-type";
   const inputs = new Map<NumKey, HTMLInputElement>();
-  const fields = el("div", { className: "e03-panel__row" });
+  const fields = el("div", { className: "e03-support-fields" });
   fields.append(sideField.root, typeField.root);
   for (const key of FIELDS) {
     const f = createInputField({
@@ -295,6 +295,6 @@ export function buildSupport(o: SupportOptions): HTMLElement {
       rec.support_forces?.[o.condition],
     ),
   };
-  requestAnimationFrame(() => canvas.render(draw));
+  canvas.render(draw); // 붙기 전 = 기본 폭 · 붙으면 ResizeObserver 가 다시 그림
   return host;
 }