I think you would do just fine wit a 5' tek over your 72" tank. That is just 6" on each side without lights directly over it. You are going to get plenty of reflection if you keep the sides clean. But that would be if you were picking it up used. 2 36s wuld be better anyway so you are not wasting light over the center brace.
is about to boom. My 48" fixture has 24 actinic royal blue leds and cost less than $100. I am building a 40 for my solana soon. These 3watt leds put my reefbrite to shame and that thing looks great on my 8gal pod.
is about to go the way of UGF
and bioballs. Lol