Mikey,
I think your a bit confused. If it fits, it fits...it won't magically tear through the fender one day. There isn't a "well it just barely fits, so something bad might happen one day". It does, or doesn't.
235/40/17 fits, and there is still room. (It fits regardless of ride height) The question is will the 245 squeeze in there, which hasn't been proven yet. If it does, it'll really help curtail the curb weight of the car and pay massive dividends in performance
.
If you think 245/40 is crazy...talk to the rx8 guys who put 275 hoosiers on their 18x8's.
I'll be testing 245/40/17 fitment by removing the rear springs and maximizing suspension travel with the wheel/tire in place. If it hits, it don't work...if it doesn't, it'll never have a problem.