Looks good! I would put myself at ease if I had at least one middle support 2x4 in there. Looks well put together! Can't wait to see it finished.
Mine is all done and pictures will be up hopefully in the next week. I decided to have the canopy built for me. Right now I've got my 55 tank sitting in my living room right next to my 25 which is sitting in front of the tv. Can't wait to get it out of there.