I'm fairly certain that I took out two layers of 3/4 inch plywood. The transom did measure 2 inches on top and in the keyhole cutout. I only have about 1 5/8 between the engine mount stringers and the fiberglass. It's about 3/8 thick and the inner skin was about 1/8. I could use 3 1/2 inch layers. I was thinking about making the seams in the wood vertical but horizontal seams may work better. Hopefully Menards will take the 3/4 back and for 1/2 plywood. Also the gentleman at express composites recommended I use 1.5 oz mat for everything.