That's a bit close to be sure. The first concern is heat. If you are venting the light well then it may not be an issue. Others will know better. You can also find the answer in the lighting stickies. You could LST or SCroG to reduce height although that plant count would make it pretty labor intensive.
bigsby Reviewed by bigsby on . heres all the info...now whats up wit my leaves?? I'm using a thousand watt high pressure sodium bulb which is well over two feet from the plants.I have a two by tree foot enclosed reflector that is attached to silver ducting and an online fan, which pulls air through my carbon filter. My thousand watt light is on a 12&12 schedual as my plants are flowering. My medium is soil, sunshine mix #4, wich has no muted in it at all. I feed my plants their bites manually and seperatly. I'm using Advanced nutrients sensi bloom parts a and b. Also in the Rating: 5