New cab, suggestions?

Ok, I am thinking of building a new grow cab. For a full grow. I want the cab to be between 7.5 and 8 feet. Probably go with 8 so there is less cutting. I drew a simple picture. How many inches between light adjustment? My Bubbleponic system sits @ 18" high. So I was think 30", exactly 1 foot from the system. Maybe thats way to close, maybe foot and a half or two feet. I don't know that's why its posted! Thanks guys. Just to reiterate, My question is, How should I arrange the lighting support beams to best suit my lamp and grow.




This is what I have in my head. The green bars are what I need to figure out. How far apart should they be? Any and all comments or questions or suggestions are appreciated. Thanks again.

You should hang the lights. Chain gives you a very fine adjustment of 1" increments. Go checkout some of the pre-made cab's it will give you good ideas. My cab has light suspended by chain and flexible ducting to in-line fan.