are u using an enclosed reflector, along with the direct exhaust blower? cause if so you can put the light even closer, but nothing less than 8 inches. My 1000 watt hps is about 10 inches from the top of my plants, and i have never had any sort of burn form the intense light or heat, but my reflector is encased, and i have a blower specifically for the light. Along with fans pushing the heat away from the plants. But if you dont have an enclosed reflector, it would be best if you kept it 10 to 12 inches away.