I have a Swim platform on my 31 Commander. It was build by a PO, it is made from 1 1/4" Marine Plywood and West System Resin Coated with some sand to provide traction and 3/4"x 20" blocks at each Horizontal tube. It was solid, which appeared to not be a problem when she was stored and Run on the Delaware River. I have it on the Chesapeake Bay and I had to cut 12"x1" slots in between the Horizontal supports to provide relieve of the water pressure pounding agaiinst the bottom of the platform and ripping the screws out. It is mounted similar to Dunroin, using 3/4 stainless tubing bolted to "U" Shaped Brackets across the transom for Horizontal support and 3/4 Stainless Tubing at a 45 degree angle from outer edge of platform to lower on the transom for Verticle support. There are wood screws going thru the tubing into the wood blocking, witht the pressure of the water pounding against the bottom of the platform while docked during severe storms the screws would rip-out. After cutting the slots and reapplying West System resin, last spring I have not had a problem. You can see it before cutting slots on my web site linked.