Its not the thickness of the wood that matters so much but also how its supported inside the fuselage. Make sure there are plywood doublers right where you are planning to glue the piece of wood and use triangle stock to secure it to the fuselage. It shouldnt be too hard to even use the same method that was used on the trikes. Use a drill, get some basswood stock and epoxy to the inside then attach the original landing gear at anywhere from behind the firewall to at least 1 inch ahead of the center of gravity.