[jyl]

The aluminum bar stock will be on the upper side of the fiberglass lip, so not between the tail and decklid. So from top to bottom, it'll be: nut, washer, aluminum stock, tail, rubber, decklid, washer, bolt head.

Interesting idea to fill the voids, okay I'll try that although I've never done anything with fiberglass. Maybe there's something easy to use at the hardware store.