I am going to build a canopy for my 50 gallon tank. The dimensions are 36x18, and I am thinking of building a frame out of 1x6's, so that 2 inches of it hangs down on the outside of the tank to cover the 2 inch plastic frame. Then putting a solid top of either 1/2" or 3/4" insided the 1x6 frame, leaving about 3 inches clearance from the top of the glass top to the underside of the canopy top. I am getting a ballast and just mounting T8 endcaps for lights, so there is plenty of room for the T8 tubes under there. Depending on the heat it puts out, I might mount the ballast on the outside of the frame in the back, or possibly at the underside of the canopy right near the back where I will have to leave a few holes anyways for the filter. Anyways, I was wondering if a sheet of plywood would work for the top, or would that warp? My glass top is hinged at about 7 inches from the front of the tank, so I guess I would have to hinge the top at the same point, leaving 11 inches that is solid that I can mount the lights too. Does this sound like a good plan? Kind of a long post just to find out what type of wood to use for the top, but thought I'd explain the whole thing while I am at it!