I'm looking at doing somthing like this for my 55 gallon. I think I'm going to go with 2 2' fixtures rather thAn 2 4' fixtures. What made you decide to use the 4' fixtures? Great progress btw. I think anything made diy is more practical and self satisfying!
I would have needed 4 2' fixtures to do what I did here, I think; unless there are 2' bulbs with the same output as the 4'. Honestly I did this one in such a seat-of-the-pants manner that I never considered 2' fixtures. I was at Lowes for the 27th time hemming and hawing over what to do, and saw that those 4' fixtures were about 22 bucks apiece, and right beside them was a case of 12 T8 6500k bulbs that would fit. Price on that seemed pretty good. So I grabbed it all and brought it home and started figuring out how to fit it over the tank.
I think hanging them might have been better. The removal of that lid to move things around and add fish and water and filters and stuff is really a pain.
If you can do it with 2' fixtures I'd say give it a shot. Those would be easier to lift and move.
I'm still trying to figure out a way to do something so that I can lift my hood and have it stay in place. I think hooks and chains would work great but it'd probably look pretty crappy.