Unfortunately my camera stinks, so only two pics worthy of posting. One that didn't make it was just of the equipment I used - a rotary tool with a side cutting bit (like a drill bit) for heavy removal, a grinding stone for lighter removal, and a sanding drum for finishing.

Right now I have the countersink screws in there, they are lighter and give more clearance for the prop adapter, I'm just not crazy about countersunk screws against the non-countersunk silicon board; not sure what will end up there.