2ft vs. 4ft T5 fixtures

[orchidjunky]

I have a relatively small collection. 4 paphs, 1 phrag, 2 noid phals, a noid onc and den. I really only care about my paphs and phrags since the noids were more or less gifts that I'm just maintaining and I never throw away plants. Anyways I've been reading that light is less optimal at the edges of a fixture so i'm wondering if my setup is good enough? I keep the slippers in the center and all the ones I don't care about at the edges. These are HO T5s that supposedly put out 8000 lumens. My plants are about six to ten inches away from the fixture. I'm thinking that for such a small number of orchids this should be enough.

Thoughts? Input is greatly appreciated..