If anyone is interested, (
@Dana Riddle) I took a series of PAR readings on my 38 gallon bowfront. I'm running two Kessil A160WE Tuna Blue lights. Readings were taken at 50% color and 100% intensity. The tank is also full of rockwork, has an overflow box, and a 2" reinforcing strut along the top of the tank running front to back.
All in all, pretty good numbers - I'm pleased. I can definitely grow SPS in here.