I'm looking for panels, preferably around 1400x2000mm, that are smooth on one side, can be painted, and VERY lightweight. They don't need to be wood, as long as they can be glued or nailed when installing. A standard brown 3mm board, 1200x2440mm weighs 8kg, which is far too heavy for my purpose. I'd like the weight to be at least halved. I'm thinking of some form of foam that is laminated on one or both sides? Any tips? (The thickness should be max 10mm, and of course, not at crazy prices) 