I'm probably just shy of 1/2" and have felt the rear slip out a couple times over a paver stone crosswalk I hit often. The rear communicates well when slipping and it wasn't very dramatic...
However, it's not the grip stopping me but finding the center stand in a high-speed bender. I mean, it is a sport tourer and I use it for utility as much as enjoyment. Actually, today was the first time I ever lost confidence. I was on a long sweeping right hander and the back end got chattery. I wasn't at ludicrous speed and the bags were light. There was a nasty split seam in the concrete that I had to correct over a couple times but I felt if there were a car behind me it would have noticed the back end hopping around quite a bit. It was windy but I don't think that was a significant factor.
Overall, bike is like a scalpel when handled correctly. I find the looser/lighter I keep my arms/hands/butt, the better it corners. So far, I've only drug a boot tip have way too many low sides under my belt to scar this pretty machine.