Also, we used to race a ZXR250 that had a 18 inch rear stock and fitted a 17" rear. We raised the forks higher in the triple clamps to accommodate the drop in the rear (lowering the front).

Maybe measure the distance from the bottom of the rear blinkers to the ground and try to duplicate a similar drop measuring the front blinkers to the ground. I know it's not ideal geometry wise, but if you end up getting a taller profile rear tire, it might be a minimal difference.

Dana