Here is another thought for accessing the tank for feeding yet have the canopy rest directly on the tank top.
On my current 55 I have a similar box but with 4 48" standard flour. tubes. It measures almost the same depth as the tank hence there is no room for access. So to get around this problem I placed 3/4" weather sealing all around the bottom edges of the canopy (prevents the canopy from sliding) then used 2 1/4 x 1" x 8" pieces of aluminum mounted on the right and left inside of the front of the canopy so that they swing down (they are mounted close to the bottom edge with a single screw centered all the way at one end). Each has a small bend in one end which makes it fit the front top edge of the aquarium. I added a small aluminum cabinet handle to the front of the canopy.
This way I can lift the canopy with the handle then slide the 1" x 8" braces down which mate with the front edge of the tank. This gives just enough clearance to open the glass tops on the tank and extract water for testing or feed. Also there is not a big change in the lighting for the fish and you maximixe your light on the tank since the lights are as close as you can get them.
Just some thoughts.
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein (1879-1955)