2" is waaay to close..mr west is rite...put ur hand at the top of ur plants...if it doesnt burn the "back" of ur hand then the plants should be fine...or u could get a thermometer and hold it at the top of the plants and know the exact temp..anything from 70-80 is good! i have a 600 watt hps.mh and o keep it about 18-20 inches from the top of my plants..good luck hope this helped!