The platforms I built the previous summer had spent a few months in the sun while being stored on the trailer. And the epoxy finish had checked badly. I thought the UV-stable epoxy from Duckworks had failed. But some research told me that Douglas Fir plywood always checks and should be covered in fiberglass.
So I set about adding fiberglass to all four platforms. I added fillets along the stiffeners in the center of each platform so that the fiberglass would have a smooth bend. With the glass glued down, I added three more coats of epoxy and sprinkled non-skid powder into the last coat. I used a UV-resistant epoxy from Raka.