T5's are a little hotter than T8's, (orT12's) T-5 ballasts optimal running temp is 95*, where as T8's is 78* or so but not much difference, if I was shopping for tubes I'd look at T5's.
I keep 4 bonsai moms and any rooting clones I have under an all blue 90W UFO, I think it would even veg 2...