Cool idea, Tim, looking forward to seeing how things work out. oobe might be right though, how cool is your cooling air? Summertime might be a royal pain in the ass. Growth just slows right down above 32 I think, and the tops get fried and crispy.
What about a 250, or a dimmable ballast. I have heat issues myself, and a small low space, and I have a full on set of exhaust fans and cooltubes, but still battle with heat. Im thinking of dimmable ballasts, and seeing if I can still get the yield with 250s instead of 400s, at least for some of the flowering cycle.
Just 2 cents....best of luck