This^^^. I wish my basement had another 2 feet. At least a foot. Iam at 7 now with 8 750 Gavitas. And the fixtures are between the basement floor joists. Got lucky and they happen to fit just snug. Nanos with the flat horizontal orientated ballast would of been even better but they would of been even more recessed...shining on about an inch of joist wood...lol. (Sawzall on a rental home = been there done that. Many landlords are pissed in this town). Truth is..I actually am too low for double ended hps. My plant heights are critical. No room for error. And canopy management is critical/ veg size is of the utmost importance. Yes...with de's...its easy to fry the tops. I have to train them low and wide in my veg room. Much more important than mogul socket hid's. 8 foot plus minimum for even 750's and I'd venture to say 2 or 3 ft more with thouie de's. But if I keep them low and out of the danger zone...Iam ok. Cant run drain to waste tables either. Just plumbed together catch saucers for runoff. Lowest I can go. Every inch is prime real estate. Again..ive said it before..and ive heard of it but I dont understand how people are cramming 750 and 1000 watt de's into tents and low ceilings.