looking at a couple of different sites it appears the smallest rear tire right now is a 170/60. I believe stock is 160/60. Do you think there would be any clearence issues? looking at the swing arm and exhaust it would have to be very tight.
I can't answer that. But, if I was buying just now, I'd look for sales on the PR2s. I think Motorcycle Superstore is discounting them. Wear them out and then get a reasonable price on the PR3s after they've been out for a bit. And then wear those out because it's just too much damn fun!