With the light fully extended, it's currently about 11 inches off the water surface. My evaporation rate has been 1 cup per day, but I do top off in AM before work and in PM after work. About 1/2 cup each. My SG usually changes by .001 - .002 between top off's. I keep it set at 1.023. It normally tests 1.024 - 1.025 depending on evap.
I'm hoping that small fluctuation doesn't effect much once it's stocked, but we'll see. I had the tank made at an LFS. They have 3 on display, and they've stated it has not affected anything they have in the tank...polyp, shrooms, zoa's etc. Of course, I didn't expect them to say otherwise, so we'll see what happens.
As for temp, that's been a slight issue, but not as you would think. The light, which I expected to be enough to heat the tank, is not doing that. In fact, it only raises temp about 4 - 5 degrees above room temp. So, I get no warmer than about 74-75 degrees for water temp, which I was not expecting. I'm probably going to need to add a small 6in heater in there for the extra 2-3 degrees, plus differential for when the light are out, because my temp then dips to 69-70.