Here is the method I used to resolve the problem of how to use three flourescent four-foot fixtures in a small amount of space. I'm sure it's been done lots before but have not seen a photo so thought I'd post one. Made the shelfs about 54 inches long so there's a bit of clearance at end of each light.
If I made another I'd have the shelfs closer together but that would depend on what you're growing (plan ahead so distance is sufficient even if you then have to lose a shelf). If your growing sarracenia you're going to need more room then flytrap seedlings! Cost me about $25 in wood. Used a emergency blanket on the back with a piece of cardboard behind it to keep it from "parachuting" with any breeze.