4 inches by 8 inches? seems like a lot of trouble for small panels.
some big-box hardware stores sell 1/2" and 1" anodized aluminum U and L channel, plus anodized strips and other goodies. Check near where they have garage cabinets and pegboard. Come to that, some track for sliding glass/ shower doors might work, too. Add some of the round plastic beading used to mount window screens in aluminum frames and you're on your way.
Remember to use stainless hardware to avoid galvanic corrosion. (also be real careful about letting copper remain in contact with aluminum in the presence of water. . . !)
remember that aluminum and glass move at different rates as the ambient temperature changes, and leave plenty of slop.
Others will have to advise on the pros/cons of backing the panels with anything. . . . there might be a heat build-up question there.
-Dan