octathingy: adjustments to the shock mount external ring

Octathingy_mount_pcb.scad

@@ -918,9 +918,9 @@ module octa_shock_mount_external_ring(height, radius, corner, gap) {
     for (rot = [0, 90, 180, 270]) {
         // anchors for rubber bands
         rotate([0, 0, rot + 45]) {
-            translate([radius + gap + 3 * ring_wall, -7.5, 0]) {
+            translate([radius + gap + 3 * ring_wall - 1.0, -6, 0]) {
                 minkowski() {
-                    cube([4 - 2, 15, ring_ext_height]);
+                    cube([4 - 2, 12, ring_ext_height]);
                     cylinder(r = 1.5, h = thin_mint, $fn = facets);
                 }
             }