I bought the kit from Mike Griffin laser cut by RSM. The plans show laminated leading and trailing edges that fit into notches in the ribs and 1/4 square for the spars. The designer used 1/4 square for the spars and 3/8 square for the leading edge, and 1/4 square for the trailing edge with 1/16 sheet over that. Pretty standard. If you are scratch building one the flaps have an arc for the trailing edge. I tried to figure out the arc and it's about 10 feet. Maybe RSM would cut a short kit.