I've added a new squat cage built into a 5 layer lifting platform and a 24" jump box made from the platform scrap. The top surface of both is made of birch topped 3/4" plywood. The platform's bottom two layers is 3/4" CDX plywood. Then comes the rack bolted into the platform. Next is 7/16ths OSB, 1 sheet of 3/4" plywood and finally the stall mats on the outside edges. In the center is the same with the top being the birch topped plywood. Sanding and polyurathane over the stickers to the tune of about 8 coats gives the finish shown.