Need help to set up a small growing system

I am planing to set up a brand new growing system, I can have baby plants from my friend, and I already bought a 4 lamps commercial fluorescent T5HO High-bay fixture, how high I should hang this fixture on top of the plants? My Friend use HPS lights, he doesn't have experience on the Fluorescent lihgts, Does anybody can give me a suggestion? Here is the fixture I have right now:

http://www.canadalite.com/Fixtures Accessories/Commercial Industrial/Fluorescent High Bay Fixtures/4 Lamp F54T5HO High Bay Fixture UNV

Thanks a lot!

as close as you can get it without burning the plants,fluorescents dont create intense lighting like hps and MH lights do, if you hang it too high your plants will stretch too much trying to reach the light, start at about 2" to 3" away, also find a small fan you can point at the light to cool em a bit.

Thanks BrownEs,

Your link is very helpful.

A high bay fixture is meant to hang on the ceilings of warehouses and retail stores. I dont know how it differs from standard lighting but you might want to look into that.

I saw some hydroponic stores use highbay fixtures to grow flowers and plants.