lighting height?

[half5.0]

Is there an optimum height for lights. I have a 55 gallon with dual 65 watt 50/50 power compacts. right now they are on the rim of the tank. Next week Im adding another pc with dual 65 watt 10,000 k bulbs. I was trying to come up with some kind of canopy so that I can run all the lights and still have access to the tank without removing a light. Any suggestions?

Matt