Is your 92 gallon a corner unit?
Only reason I ask is because a T5 unit will be difficu,lt to fit over it, since you are limited to such a small fixture over those tank I would recomend a single Halide, it would end up looking nicer I think.
Some corner units have more of an open top, while others have a bunch of plastic on top of them. I would recomend two if possible, but I know on some models it isn't.