Here's my solution.
It really wasn't that much work once I figured out how to do it. The 'mold' is made out of a plastic bottle and some scrap wood. The lay up is 4 layers of glass and one layer of carbon with epoxy and some micro balloons to make the epoxy more 'past-like'.
The result is light and very rigid. I ran a few tanks already and the engine remains rock steady. Hopefully first flight this Sunday.

Greetings,
Jock