Ah yes, so they do!
I guess my concern is not really w/ the stress and use once installed, rather what happens when you are crimping them into place.
I have never installed one, just seen them afterwards and seen many pictures of the installation method now. But basically they get drawn up towards the surface, splaying the sides outward and creating a ring on the backside, right?
I'm just thinking that in order for that crushing to take place, this must be a lot of pressure around the hole in teh fiberglass. I guess I'm just paranoid. I guess the key is to esnure the fastener used is the correct depth for the material, so teh aplaying is mostly below the surface and not inside of it.