The window came from a manufacturer called "Creative Windows", which, of course, in out of business. I have no idea what kind of shell it was in, nor did the owner of the shell...it was on a 96 fullsize chevy pickup, though. In the second photo, leaned up against the sawhorse, is a silver "D" shaped flange, which is what the frame screwed into on the shell. To get that piece in, though, I would have to cut a lot more fiberglass out, so I think I'll go with the sheet metal screws into the metal. If that isn't sturdy enough, I'll have to run bolts all the way through and put a backing plate on the inside of the shell. The outer marks on the top were where I marked it with the inside edge of the flange, so you can see I'd clearly be in the hollow part of the shell had I made those cuts.
Thanks for the locate on the steel strip in there...I was figuring those rivets went to something solid, but also thought they might just be there to hold the window felt in. Do you know how thick that steel band is? Is it sheet metal or thick enough that it will serve as an anchor for the screws? I'm assuming if it took a nut being welded to it, it's probably pretty thick. Is there a diagram somewhere that has the layout of the metal in the top? Like maybe someone has x-rayed one before at a border crossing or something? I didn't see anything in the resources section.
For adhesive, what do you think...epoxy? I don't know of much that bonds to aluminum very well. even if it's sanded rough.