Cross post from Home DIY:
Types of plastic/acrylic/perspexy materials:
What is the lightest weight and strongest / least likely to flex/warp?
What is not stupidly expensive and easy to order more of in the UK to the same spec (4x4 and 8x8 sheets with clean edges - or if the edges are rough they can be polished/sanded down by me)?
What can I screw into so it has a metal frame of some kind?
What would glue well to ply (so I could glue a sheet of ply to one side and the metal frame screwed into the other) and not peel away over time despite exposure to extreme heat and potentially bumps?