Perhaps textured acrylic? I haven't tried it but it may be a solution... it's a good idea I may use it someday. The thing would be to figure out the 40 lb per square foot (in our area) to the thickness & size of the sheet. I know I've seen some acrylic stock in the HDepot but I don't recall if you can get it over a 1/2 or not? I'm sure someone online makes it though, let me know how you make out.. it's an interesting idea.