i would go stock gt2 sizes with rolled rears, or 18's w 7x15 spacers if on oem twists. but a 9x12 w a 40 offset BOTH front/rear is wickedly stable.

best i still have yet to find is the std gt2 setup with the 40/45 offset and the 8.5 up front. i have tight corners and the 9" would sled.

also.. way i go thru rears? its no longer worth the cost of ps2's though i think its the better tire. the better ( best ) value still for me is the p zero in the gt2 sizing.

 

honestly I like the current look and wouldn't change it. If you need a track setup just buy an 18" wheel with dedicated race tire and swap at the track.