Aluminum, steel, stainless steel, fiberglass. I think between all the manufactures they have used them all. Aluminum is light, but unless its 1/8th inch it gets wavy. With any material, thickness increases rigidity.
The glass is real heavy safety glass like a car windshield. We once threw all the glass from a fishbowl into a dumpster, the garbage truck couldnt lift it. He estimated it was nearly 1 ton. That sounds like a lot, but each side glass took two guys to lift down, they are not light, and there are 8 to 10 of them in a Bus, plus the windshield, back glass, and front driver side and door glass.
My plan is to keep the window frames but replace the glass with lexan or some kind of polycarbonate, or possibly aluminum panels. That will keep it looking like a Bus, but it will lose a lot of weight. If I screw them down from the outside I wont have any trouble doing repairs.
