I use t5 only. I LOVE it, as do the coral.
I would do 1 bulb for every 3" of width. 8 bulbs!
What bulbs and combination are you using?
I am doing retrofit and will need two more ballasts. I now have two Workhorse 7 ballasts and am considerint ATI ballasts. Any opinion on ballasts to drive 80 W t5's?