Just don't get too close, I have no experience with non air cooled, I use 3 600's that are glass sealed and have air pumping through them at a very high rate. That reflector of your looks like an antique...lol. I go about 5-6 inches above the tops. A foot is a guess for you, may be closer or further. The leaves will start to twist if too close or in extreme cases burn. also the flower would start to bleach (tips turning white) if too close. That plant will basically speak to you, you just have to figure out what its saying. True with watering, nutes, air, light, etc.... And all strains want something a little different though, one strain may explode under 1800 ppm nutes where another one is burning. Examples, blue dream gets botrytis at low humidity, og kush gets powdery mildew ALWAYS, my purple trainwreck has tips burning at 1350ppm when everything else is fine....you get the idea.
The light distance will be a function your light/reflector setup, temp in the room, air flow and strain. So when you read that a 400w needs to be "X" inches away, it kind of meaningless. the correct distance is as close as you can get it without it being too close. Sounds cryptic, huh?