i think it'll work just fine. once you get goin, of course, you'll have your tweaks here and there but, imo, i think youve got a good base working there.
also, about temps.......
you mentioned you are playing around with the idea of CO2.....?
CO2, imo, works better in a slightly warmer enviornment so drifting a lil higher than the 78F youre getting now would be just fine, imo. but not sure if your plans changed there....
also, if, your planning on using it for a veg chamber for outdoor plants, this, also, would help them harden off for the impending summer temps.
anyways....
i'm looking forward for more updates....
-side note-
ever try laying one of these 4x4s on their side and use for a veg chamber with T5s?
works GREAT if youve got ALOT of clones and only want them 12" or so before they go out. you can fit ALOT more in there when its on its side.
but that would be for another day, i suppose....
anyways, rock on farmer t.o.
-cap