It's mounted over a JBJ RF-25 @ 8" off the water and no reflector, per BRS recommendation. I do use a glass top, so I'm expecting 10-20% reduction in par, but I'd still like to make 200 on the sand (16" of water). I'm not messing with the spectrum at all, other than just turning the knob to where I like visually and letting the kessil logic work out the rest. Anyone else have one mounted over a similar sized cube? My plan was to start at around 40%.