I finished the removable section in front of the Fuse box yesterday. I needed to add two pieces of styrene to shim a bit of a sideways wiggle due to a bigger gap than expected with the triangular key pieces. Now it fits perfectly and is very stable. All this will be topped with the 1 1/2 pink foam I've been using. I'll probably use a hot knife to get a nice separation of the foam for the removable section. This way it will remain easy to lift out for when someone decides to use the George Foreman Grill and Toaster at the same time.
Photos below.