hey rich....
I am picking up a different question than is being answered.. My answer would be...
T5's are best suited for clones. They ARE good for veg to a certain point.. I wouldn't go bigger than 12" but you can keep spacing pretty tight by keeping the lights low.. I mean on them almost. A fan will stop what little heat that isn't dissipated to not hurt your plants at all. I have 3x 4' sets that I keep 6" apart. I have a HPS I keep mothers under.. not ideal, but I will get a MH when this bulb goes.
If I read it wrong too, sorry man.. but I think that's what you meant.