I am running the stagered size that you are "leaning" too with 275 on the rear. I am running NT05's and you get a little rubbing on the fronts in thigher corners and under compression but not bad and after you wear some tread away (2-3 session depending on how hard you run) it goes away. I am happy with the setup but I am planning to drop to 18's and square set up when i wear out my current set of tires. Unfortunately they only have 1 event on them so I'll have to wait awhile. My reason to going square is the same one's you listed in addition to the fact that 18" r-comps are much cheaper and readily available than 19's.
AW 1M #43 USA
Meisterschaft, N55 mids, AFE CAI, ER Charge, Wagner IC