I was just at a consultation where the guy wanted to place a 265 gallon tank on the third floor. I dont know if you guys have seen the new engeneered beams, but we needed to find out if it could support the tank and the rest of the stuff on that floor and they said that the new beams can hold 2000 lbs per 18 inches. I believe, that its that much. Pretty close anyways. Point being that you can really do some crazy things with just plywood. My big thing is look how its made by the pros and anything more is just beefy!