Once my clones root, and i transplant them to pots, i put them directly underneath my 400watt mh...Im not sayin slam the light right on top of them....i keep the light about 3 feet from the top of canopy and i have no problems...so if u drop ur light down to 400w u should have any problems...i dont even think u would if u ran it at 600w, but like i said, just keep it up of the canopy, until the plants get acclimated to the light, then drop it down...hope that helps....keep em green...-ganja-