That's a great looking tank! Well done! How do you find the added lights? I have 3 x XR15 g.6 on a similar sized tank with consideration for 2 x AI Blades on the side (... i have actually bought the brackets already!)I added 2 more XR15s. The outer 2 are the G5 and the inner 2 are the G6. I put the G6 in the middle due to the wider spread the newer lenses give. G5s on the edge to reduce light spill.
What sort of PAR are you getting in your tank?