Will came by with a 70s knee board with this flexy fiberglass tail. He wanted to make something new utilizing a flex tail. I recommend using wood as the flexer. I think wood has better flex characteristics than resin and fiberglass.
The question was how to get the wood on the tail. Answer, laminate a whole sheet of wood to the bottom of the board. Note, the Bluegill rails on the foam board.
With the help of Tyler Olsen, we vacuumed on a thin sheet of wood.