I'm launching my new Sea Rider multi-chine tomorrow. My 4th boat, but my first Yost. I used 2x half inch rings of marine ply for 1-inch rise, considering I might one day want to try a sea sock, and Mr. Yost has said 1 inch is best for that. Otherwise, I would have considered a single 3/4 inch ring of best non-marine I could find in 1/4 or 1/2 sheet.

I used fairly decent piece of non-marine 1/4 inch for the top ring, purchased as a 1/4 sheet at HD.

I widened the bottom, permanent ring to 1 inch wide, for a little more beef.

Be sure you get the most economical use out of your marine ply. I easily got 7 bulkheads and 3 (admittedly small, at 16x24 inch) combing rings from a 4x4 foot piece, and had more than enough left for stem plates. The other 4x4 foot piece was used by a friend who got 8 bulkheads and 3 full-sized combing rings out of it.