Have to agree... 1' square per pot, so that would be 8 crammed under a t5 (8bulb) footprint (2'x4')... need x3 ballasts minimum + still have 1 pot sitting way to the outside...
Here's something else to think on... the t5's w 8 bulbs is going to crank out some heat... a lot of heat. You can't vent the hoods, so you gotta really cool that room or vent the entire place a lot. I wasn't ever able to run all 8 bulbs w several ballasts.
In veg (& this is slower growth, not looking for fast), I'd put 6 buckets under each ballast w 4 bulbs firing, spaced apart w/in the ballast. Again, just to offset heat issues, went less light. By these numbers, you would use 4 ballasts & still have one pot out. The last 6" on either end of the ballasts gets much less light vs the middle 3'... just to note.