Thanks. The odd shape is just to stay within the flat sections of floor. it's 3/4x3/4 square tube. I'd probably go to 1x1 if I did it again for more clearance to the wire connections but this works just fine. The picture isn't with the tank fully tight but it fits well. The top piece is just some 16g sheet metal held down with drill screws. As always, more than one way to do something.