A 315 in a 3x3 is perfect I've run them like that for quite some time now. Mid flower maybe 18 inches or even a lil closer if I can get it. I do the old school back of your hand test to check for heat and have only had one small spot of light bleaching, way smaller than even a dime. I personally think every smoker should have a 315 and a 3x3, it's the best personal use setup I can think of.