275 on a 9" wheel is exact spec for width according to discount. You will not rub unless you lower your car over an inch. I'm running 275x35x19 on a 19x9 F and 305x30x19 on a 19x11 R with around a 1inch drop.
Don't be fooled, handling characteristics will improve. Nissan would dip into their profits by putting wider tires/wheels on the Z. I would say try to avoid increasing the stagger though. On a side note, it looks like there is plenty of room for 315s in the rear if you want a more aggressive look.
