For those of you who have added plywood to the top of your aluminum bench seats, how thick of plywood? 1/2, 5/8, or 3/4? I am leaning towards 5/8 (splitting the difference) because I am also adding seat bases that will connect to the plywood via tee nuts installed on the underside of the plywood. The plywood will be attached to the aluminum bench with bolts and plus nuts.