diff --git a/public/js/webgl-book-shape-lab.js b/public/js/webgl-book-shape-lab.js
index 63f51e0..d75111f 100644
--- a/public/js/webgl-book-shape-lab.js
+++ b/public/js/webgl-book-shape-lab.js
@@ -68,11 +68,12 @@ const OPEN_SEAM_GAP = 0.003;
 const PAGE_COUNT_MIN = 40;
 const PAGE_COUNT_STEP = 10;
 const PAGE_WIDTH = 1.62;
+const PAGE_SPLINE_LENGTH = 1.955;
+const PAGE_LINE_SEGMENTS = 24;
 const PAGE_DEPTH = 2.24;
 const COVER_OVERHANG = 0.13;
 const COVER_SUPPORT_OVERHANG = 0.055;
 const HINGE_INSET = 0.07;
-const MAX_SUPPORTED_STACK_RISE = PAGE_WIDTH * 0.5;
 const SUPPORT_ANGLE_STEPS = 720;
 const SUPPORT_ANGLE_CANDIDATES = Array.from({ length: SUPPORT_ANGLE_STEPS }, (_, sample) => {
     const angle = sample / SUPPORT_ANGLE_STEPS * Math.PI * 2;
@@ -208,17 +209,19 @@ function rebuildBook() {
     const coverDepth = 2.30;
     const coverThickness = BOOK_PROFILE.coverThickness;
     const pageWidth = PAGE_WIDTH;
+    const pageSplineLength = PAGE_SPLINE_LENGTH;
     const pageDepth = PAGE_DEPTH;
     const bundleCount = Math.max(4, Math.round(pageCount / 10));
     const spineWidth = calculateSpineWidth(bundleCount);
     const leftCount = calculateLeftBundleCount(bundleCount);
     const hingeX = spineWidth * 0.5 + HINGE_INSET;
+    const foreEdgeX = spineWidth * 0.5 + pageWidth;
     const bundleSpacing = calculateBundleSpacing(bundleCount, spineWidth, leftCount);
     activeSpineHalf = spineWidth * 0.5;
-    const lines = simulatePageLines(bundleCount, pageWidth, spineWidth, hingeX, bundleSpacing, leftCount);
-    lastLengthError = measureLineLengthError(lines, pageWidth);
+    const lines = simulatePageLines(bundleCount, pageWidth, pageSplineLength, spineWidth, foreEdgeX, bundleSpacing, leftCount);
+    lastLengthError = measureLineLengthError(lines, pageSplineLength);
     lastSpacingError = measureStackSpacingError(lines, bundleSpacing);
-    lastBookModel = { coverDepth, pageWidth, pageDepth, bundleCount, spineWidth, hingeX, bundleSpacing, lines };
+    lastBookModel = { coverDepth, pageWidth, pageSplineLength, pageDepth, bundleCount, spineWidth, hingeX, foreEdgeX, bundleSpacing, lines };
 
     addCoverAssembly(pageWidth, coverDepth, coverThickness, spineWidth);
     addClothSpine(pageDepth, spineWidth);
@@ -244,7 +247,7 @@ function addCoverAssembly(pageWidth, depth, thickness, spineWidth) {
 function createCoverAssemblyGeometry(pageWidth, depth, thickness, spineWidth) {
     const spineHalf = spineWidth * 0.5;
     const hingeX = spineHalf + HINGE_INSET;
-    const outerX = hingeX + pageWidth + COVER_OVERHANG;
+    const outerX = spineHalf + pageWidth + COVER_OVERHANG;
     const outerTopY = BOOK_PROFILE.tableY + thickness;
     const connectionTopY = BOOK_PROFILE.raisedHingeY;
     const spineTopY = BOOK_PROFILE.tableY + thickness;
@@ -380,9 +383,13 @@ function calculateMaximumPageCount() {
 function isBundleCountReachable(bundleCount) {
     const spineWidth = calculateSpineWidth(bundleCount);
     const bundleSpacing = calculateBundleSpacing(bundleCount, spineWidth, bundleCount);
+    const foreEdgeX = spineWidth * 0.5 + PAGE_WIDTH;
+    const target = restingTarget(1, foreEdgeX, bundleCount - 1, bundleCount, bundleSpacing);
     const anchor = spineCurvePoint(1, spineWidth);
-    const topLineY = BOOK_PROFILE.coverThickness + BOOK_PROFILE.paperContactOffset + (bundleCount - 1) * bundleSpacing;
-    return topLineY - anchor.y <= MAX_SUPPORTED_STACK_RISE;
+    const chordLength = Math.hypot(target.x - anchor.x, target.y - anchor.y);
+    const solverSlack = PAGE_SPLINE_LENGTH - chordLength;
+    const minimumSlack = PAGE_SPLINE_LENGTH / (PAGE_LINE_SEGMENTS + 1);
+    return solverSlack >= minimumSlack;
 }
 
 function calculateBundleSpacing(bundleCount, spineWidth, leftCount) {
@@ -408,10 +415,10 @@ function calculateLeftBundleCount(bundleCount) {
     return THREE.MathUtils.clamp(Math.round(bundleCount * readingProgress), 0, bundleCount);
 }
 
-function simulatePageLines(bundleCount, pageWidth, spineWidth, hingeX, bundleSpacing, leftCount) {
+function simulatePageLines(bundleCount, pageWidth, pageSplineLength, spineWidth, foreEdgeX, bundleSpacing, leftCount) {
     const lines = [];
-    const segments = 24;
-    const stepLength = pageWidth / segments;
+    const segments = PAGE_LINE_SEGMENTS;
+    const stepLength = pageSplineLength / segments;
     const entries = [];
     const spineArc = buildSpineArcSamples(spineWidth);
     const rightCount = bundleCount - leftCount;
@@ -452,7 +459,7 @@ function simulatePageLines(bundleCount, pageWidth, spineWidth, hingeX, bundleSpa
         let lowerLine = null;
         sideEntries.forEach((entry, rank) => {
             const anchor = spineCurvePoint(entry.t, spineWidth);
-            const target = restingTarget(side, pageWidth, hingeX, rank, sideEntries.length, bundleSpacing);
+            const target = restingTarget(side, foreEdgeX, rank, sideEntries.length, bundleSpacing);
             const points = buildSupportSolvedLine(anchor, target, lowerLine, side, segments, stepLength, bundleCount, bundleSpacing);
             const line = { index: entry.index, t: entry.t, side, anchor, points, endpoint: points[points.length - 1], isHairPage: entry.isHairPage === true };
             lines.push(line);
@@ -540,10 +547,10 @@ function initialPageLine(anchor, target, segments) {
     return points;
 }
 
-function restingTarget(side, pageWidth, hingeX, rank, sideCount, bundleSpacing) {
+function restingTarget(side, foreEdgeX, rank, sideCount, bundleSpacing) {
     const local = sideCount <= 1 ? 0 : rank / (sideCount - 1);
     const foreCurve = 0.11 * Math.sin(Math.PI * local);
-    const x = side * (hingeX + pageWidth - foreCurve);
+    const x = side * (foreEdgeX - foreCurve);
     const y = BOOK_PROFILE.coverThickness + BOOK_PROFILE.paperContactOffset + rank * bundleSpacing + 0.002 * Math.sin(Math.PI * local);
     return { x, y };
 }
@@ -824,7 +831,7 @@ function coverTopYAtX(x) {
     const ax = Math.abs(x);
     const spineHalf = currentSpineHalf();
     const hingeX = spineHalf + HINGE_INSET;
-    const outerX = hingeX + PAGE_WIDTH + COVER_SUPPORT_OVERHANG;
+    const outerX = spineHalf + PAGE_WIDTH + COVER_SUPPORT_OVERHANG;
     if (ax <= spineHalf) return BOOK_PROFILE.coverThickness;
     if (ax <= hingeX) {
         const t = (ax - spineHalf) / (hingeX - spineHalf);
diff --git a/public/webgl-book-shape-lab.html b/public/webgl-book-shape-lab.html
index 0238ebb..f48a61b 100644
--- a/public/webgl-book-shape-lab.html
+++ b/public/webgl-book-shape-lab.html
@@ -74,6 +74,6 @@
         <button id="fast_forward" type="button">Fast Forward</button>
         <output id="flip_count">0 / 10</output>
     </div>
-    <script type="module" src="/js/webgl-book-shape-lab.js?v=hinge-relative-stacks-1"></script>
+    <script type="module" src="/js/webgl-book-shape-lab.js?v=spline-length-foreedge-1"></script>
 </body>
 </html>