i didnt put mine under, i mounted it on the wall beside my grow, and pointed right into the nderside of the canopy. only got one, but im supposed to have another in like monday. whats cool is if you turn off the MH lamps, you can see just how much light is thrown off of that 500w output CFL. it put out WAY more ligh t than i thought it would. im going to mount one on 3 sides of my grow. that will give me 1500w of CFL and 2000w of MH light beatin down on the girls......if im not careful there goig to start asking for mieties wit little unbrellas and some sunscreen!