I ended up raising my lights. Ya they're covered and have excellent air cooling but as it flowers more and more, the tops and the next row of leaves really do shade the heck out of the 3rd and 4th row of buds. So now I've got them about 10" away and things seem more well lit. I think if you were only using one plant per light, which I did in an experiment, it is a great thing to let them go up to 2" from a cooled hood. That plant is actually my best producer so far. But it's a waste of light.