I think a single 3/4 ply top will do it. It has no issues on my 200g tank. As far as carrying the load, yes, it still goes to the 2x4 or whatever supports, but without a solid top, it will probably collapse. Nobody on all the places I researched to make a woody attempted it without a soild piece for the whole top of the stand. Some of these guys are serious engineers, so I had no reason to test it otherwise. A sheet of 3/4" flooring grade plywood was like 20 dollars. Well worth it IMHO.