I installed an
awning Rail on my 1973
LoveBug.
I used rivets which were the right length to reach through the rail and the fiberglass only. I then coated the backside of the rail with silicone and carefully drilled through the fiberglass without going through the elephant hide. Then simply riveted the rail to the shell. There was no noticeable impact on the elephant hide. It did stretch a little when inserting the rivet but rebounded as the rivet was compressed.
I probably used more rivets than needed out of caution, but we installed a bag awning and left it in place during towing.
This project was done many years ago and is told from memory.
I do remember that I could afford to be careless with the drill when the rivets went inside the closet!
It was odd but every time I left home or a campsite, the bag would flip up and lay above the rail. It would then just stay there until the next time it was deployed....