Being able to do hot work with aluminum would open up a new world of possibilities, but it's pretty hard to argue with $20 for a header that works.

Here are some shots of how I made the fiberglass and CA servo hatch covers. I got a shape that I liked out of balsa, with modeling clay fillets. Then I spread medium CA over it and sanded off the fuzz, being carefull to not disturb the clay. This is done to allow the clear packing tape to stick, this is my quick release barrier. I also waxed the tape. Then it is a simple matter of spraying a tack coat of 3M77 on some cloth and form it around the plug. Hit it with mrdium CA, sand and follow up with a second layer of 2 oz cloth. That's it, peel it off the plug, trim and sand.