No problem, like I said I have lenses on all of mine and I run air.
Them tops can touch the lens and not get burned.
I kid you not.
I also have a small turbo fan in there blowing straight up at the lens.
Without air and lens I’d hate to venture on how far for you cuz I’ve never ran them any other way
Before I moved I ran k’s but that was in an open area, there again it was the same hood as what I’m running now just different ballast.
I’m also using smaller tents with a 600 and have no problems.
2’ square tempered glass $15
Inline 4" fan from Menards $15
4- 4" elbows and a 4’ piece of alum ducting $10
Priceless
Wintertime I use heat mats on the pups, bigger plants seem to be handle a bit cooler.
Just keep their tootsies warm, you’re good.
I’m at a constant 72
Ceiling fan to get that heat off the ceiling