Thanks for the kind words.
I've added a page from the Infiniti manual for the wheel/tyre factory specs. I read up on this stuff on the myG37.com website as well since the guys in the US are right into this sort of stuff. Suffice to say, 275's are probably the widest you would go on the rear stock rims.
Regarding the badges, it's tough call but I'm glad that whoever owned the car in a previous life also added the infiniti badge to the steering wheel.