Since my tank is 25" long, I made the stand 26". I used 2 1/2" deck screws and I predrilled each hole with a 7/64" bit. I probably could of went a bit larger, but it worked and I didn't split any of the boards.
I had to go buy (1) 2x4x10 to put the center braces in.
I added a center brace, probably didn't need it but better safe than sorry. I would of hated to not put the brace in there and then have the board get wet over time, warp and crack the tank. I also added another board to each corner so I will have something around the edges to nail the cover to. I haven't picked up the 4x8 sheets yet, but I am leaning towards birch but will decide tomorrow when I go back to the store.