I have not used it for panels, but for other things.
Spray expanding foam insulation is a some what decent adhesive and waterproof. Check what it says on the cans to be sure, may be various types. It's not normally UV resisant so it would need painted to protect it from the sun.
Expanding foam should seek out and seal/fill any cracks or gaps in joints and such where used.
Just a thought.
Silicon may work ok too, though fine hair line areas are hard to seal and can be missed. I have also had some things that silicon peeled loose on too easy to suit me.
If you can get it, Butyl caulking like they used to use for putting in car windshields, used to be about $10 a tube when I used it years ago. That was some good stuff, but probably don't plan to take the glass back out. It also came in a tape type roll, you could line the frame and press the glass down onto it if the frame is made that way.
I know some people that made double pained windows using it, they did not have any moisture problems.
Don't know the name off hand, there is a stuff in a tube that is clear and liquid like.
It's a bit runny when you first squirt it out then dries hard. It gets stiff and gooey before getting hard. I use it to repair gas tanks, oilpans and other things that leaked. It might be a good sealer to squirt over all seams and joints, let it run in and cure, then apply more. If you got the joints filled or covered well it should work good. When I used it on gastanks and oilpans etc to fill holes or stop leaks I put it on to the cleaned area, let it get tacky, press tape or small metal patch etc.. onto it, then coat again over that and large area around it. I don't think any of those patches ever came loose or leaked. Good stuff, sold most every where as a sealer.
Check auto stores or discount stores in the auto and sports sections for it. I think it was a yellow thin metal tube like toothepaste.
