i really like being able to open the canopy from the front. the only reason the top opens is to get the fixture out if needed. you could mount the lights to the top of the canopy on a light rail and still have doors in the front. then all you would have to do is slide it back to reach inside the tank. but i would still have the top removable for when you need to change the bulbs. or you could go with my design. the bottom of the front openings is level with the tank frame, so theres only about 2" of verticle clearance for my hand, but i can slide the fixture back. in the second pic you can see that the doors open right level with the fixture, not underneath it, so there is no glare at all. as for how high to hang the fixture, since the constellation can give you similar if not better par than some setups, i dont see why you couldnt hang it up 6", but since they run so cool, why do get it as close to the water and get the most light?
-Justin