I am not 100% sure that 1/2 or 3/4 inch marine plywood is used for the bulkheads or the cabinetry. I have cut and pre-installed 3/4 inch marine plywood for the interior port bulkhead and top. This marine plywood weighs a ton, the boat would be listing to the Port side.I think just good quality pressure treated plywood is used with that degraguard skin. The difference is weight between the two is too great. I am going to use a good quality pressure treated plywood....any thoughts on this. Thanks Remi