I corner just as hard on my Bilenky tandem which has 42mm tires as I do on my Norman which is running 25mm tires. For me, tire size is less an issue than that of knowing my limits and those of the bike I'm riding.

BTW, back when I was riding motorcycles I had a 1993 CBR 1000F and I remember doing a two wheel drift as I was cornering with the bike leaned pretty hard doing around 60-70 MPH and with my wife on the back. I can't help but think that a lesser rider would have either tried to brake and stand the bike up and high-side or give it too much bar and low-side the bike. Either would have been catastrophic since a stone face where the road had been cut out of the mountain was what would have been slammed into with a wrong move. Admittedly, a low-side would have been preferable, but not by much as it would have ruined someone's day.