Have originals, 28/29 & 30/31 that I could trace on paper for you. I've used 1/8" plywood and 1/8" Thermo Ply (by Tyco) and glued thin vinal on them and also sewed a binding around the edge. The plywood was sealed with poly before I glued the vinal on. Thermo Ply doesn't need a sealant. The reason for making my own was that comm. panels seem to warp or get a little wavey after a couple of years. My assumption was that the "waterproof" cardboard that they use is too thin and not that waterproof. You can sew both of these materials with a strong household sewing machine, but a walking foot machine makes it easier to hold a straight line. Just folding the vinal around the edges and around the back and sewing around the edges, in 3/8" or so, looks almost as good as a binding and alot easier to do.
