I had mine so the bulbs are 3" above the water. I think anywhere from 3-6" is good. Too high & you get a bit of scatter & lose some light. If you were to hang the lights from the ceiling, then an adjustable chain would be ideal. However, I think that a canopy would look good, esp. if you can decorate/build it so it looks like part of the tank/stand.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.