I run de 1kw hps in a 7ft room.
I dont have any issues at all...
I know
@Renfro is a very experienced and reputable grower around here, but my experience is differant.
I'm not saying that it may not be better to run them higher, but I have no experience in that, I've only ran them in my room.
I know everyone here says differantly... but I dont notice any differance at all in the plants burning more from a de 1kw bulb in a similarly sized se 1kw hps fixture.
I'd say right now my bulbs are 16 or so inches from my top colas, not ideal, but not a issue.
I truly dont get what everyone is on about pertaining to de hps needing so much freakin headroom because my experience just doesnt match up.
Edit, an to top it off my fixtures are on super lumens so they are pushing 1150 watts I believe...