diff --git a/src/frame-piece-top-or-bottom-aux-and-neutrik.scad b/src/frame-piece-top-or-bottom-aux-and-neutrik.scad
index 5d88c6f..edbd936 100644
--- a/src/frame-piece-top-or-bottom-aux-and-neutrik.scad
+++ b/src/frame-piece-top-or-bottom-aux-and-neutrik.scad
@@ -16,7 +16,11 @@ module top_or_bottom_aux_and_neutrik_frame_piece() {
 			translate([0, (frame_y/2)-(piece_width/2), 0]) cube([frame_x, piece_width, frame_z], center=true);
 			// ...minus the frame wall and lip on the left
 			translate([-frame_x/2+frame_wall/2, 0, 0])
-				cube([frame_wall, frame_y, frame_z], center=true);
+				cube([frame_wall, frame_y-frame_wall*2, frame_z], center=true);
+			linear_extrude(height=frame_z, center=true) polygon([
+				[-frame_x/2, frame_y/2], [-frame_x/2+frame_wall, frame_y/2-frame_wall],
+				[-frame_x/2, frame_y/2-frame_wall]
+			]);
 			// ...minus a slot for the combining piece to go into
 			cube([frame_x, frame_y-(panel_support_width+frame_wall)*2, inner_frame_z/3], center=true);
 		}
diff --git a/src/frame-piece-top-or-bottom-extended.scad b/src/frame-piece-top-or-bottom-extended.scad
index d7b25d9..bf7f7bd 100644
--- a/src/frame-piece-top-or-bottom-extended.scad
+++ b/src/frame-piece-top-or-bottom-extended.scad
@@ -10,7 +10,11 @@ use <frame-piece-top-or-bottom.scad>
 module bottom_piece_wall() {
 	// get a slice of the piece, to use it in extruding
 	projection(cut=true) rotate([-90, 0, 0]) translate([0, frame_y/2-frame_bevel_height, 0])
-		top_or_bottom_frame_piece();
+		difference() {
+			top_or_bottom_frame_piece();
+			// chop off the lip we left on the basic piece
+			translate([-frame_x/2+frame_wall/2, 0, 0]) cube([frame_wall, frame_y, frame_z], center=true);
+		};
 }
 
 module bottom_piece_extension() {
@@ -22,8 +26,12 @@ module bottom_piece_extension() {
 }
 
 module extended_top_or_bottom_frame_piece() {
-	top_or_bottom_frame_piece();
-	translate([0, -frame_y/2+frame_bevel_height*2, 0]) rotate([90, 0, 0]) bottom_piece_extension();
+	difference() {
+		top_or_bottom_frame_piece();
+		// chop off the lip we left on the basic piece
+		translate([-frame_x/2+frame_wall/2, 0, 0]) cube([frame_wall, frame_y+1, frame_z], center=true);
+	}
+	translate([0, -frame_y/2+frame_bevel_height, 0]) rotate([90, 0, 0]) bottom_piece_extension();
 }
 
 extended_top_or_bottom_frame_piece();
diff --git a/src/frame-piece-top-or-bottom.scad b/src/frame-piece-top-or-bottom.scad
index 3c75548..44fd407 100644
--- a/src/frame-piece-top-or-bottom.scad
+++ b/src/frame-piece-top-or-bottom.scad
@@ -16,7 +16,11 @@ module top_or_bottom_frame_piece() {
 			translate([0, -(frame_y/2)+(piece_width/2), 0]) cube([frame_x, piece_width, frame_z], center=true);
 			// ...minus the frame wall and lip on the left
 			translate([-frame_x/2+frame_wall/2, 0, 0])
-				cube([frame_wall, frame_y, frame_z], center=true);
+				cube([frame_wall, frame_y-frame_wall*2, frame_z], center=true);
+			linear_extrude(height=frame_z, center=true) polygon([
+				[-frame_x/2, -frame_y/2], [-frame_x/2+frame_wall, -frame_y/2+frame_wall],
+				[-frame_x/2, -frame_y/2+frame_wall]
+			]);
 			// ...minus a slot for the combining piece to go into
 			cube([frame_x, frame_y-(panel_support_width+frame_wall)*2, inner_frame_z/3], center=true);
 		}