Stiff upper lip (extend front tabs into rib)

cpu_case.scad

@@ -220,11 +220,9 @@ module lid() {
         translate([OUT_L - WALL - FLANGE_W + SLIDE_CLEAR - 2.0, 0, 0])
             cube([2.0, LID_Y_LEN, FLANGE_H]);
 
-        // Y+ stop tabs — two 10 mm tabs at 1/3 and 2/3 of OUT_L, press against Y+ interior wall
-        translate([OUT_L/4 - 5, LID_Y_LEN - 3, FLANGE_H - 3])
-            cube([10, 3, 3]);
-        translate([3*OUT_L/4 - 5, LID_Y_LEN - 3, FLANGE_H - 3])
-            cube([10, 3, 3]);
+        // Y+ stop rib — full-width cross member spanning between rails, stiffens closed end
+        translate([WALL + FLANGE_W - SLIDE_CLEAR + 2.0, LID_Y_LEN - 3, FLANGE_H - 3])
+            cube([OUT_L - 2*WALL - 2*FLANGE_W + 2*SLIDE_CLEAR - 4.0, 3, 3]);
     }
 
     color("#004B49") {