Slider rails on a floating canopy?

[dgelz]

I've got a design for a floating canopy that incorporates the use of sliding rails so I can push the canopy back to the wall for maintenance purposes and general upkeep. Is this overkill? Someone mentioned I should hang it high enough so I can still get in the tank to do work. And he was curious how I was going to hide the rails when it was over the tank.
The lights that will be mounted in the canopy are three hydra 52's and two (2bulb) retro t5kits on either side of the hydra 52's. Never done this before, so I'm looking for proper advice. How high above the tank should the canopy be mounted? Thanks, everyone