: I am looking for a way to make a smaller plywood frame in a Yost style boat.

I would make a ply thin frame then laminate a tow of carbon or glass on both edges using Bruno Meres technique of wet out the fiber than wrapping it with cheap electrical tape drilled with holes, lots of holes, to let the extra resin out. He made a carbon Bike frame with this technique. It may be simpler to start with a 1.5" wide frame and use fiber glass tape and then sand it thiner after cure. You do need glass on inside also to form the i beam affect.
Don