I've had 265-35 on 19x10.5 before and it's a stretch. I've also ran 275-35 on same size wheels and they look fine. I'm now running 285-30 on my 20x11 and it's about perfect.
It's also depends on tires as well. Some tires have meatier sidewalls than others.
Here's how my Dunlop Sportmax 275-35 looked on my 19x10.5. As you can see the rim's lip is protected perfectly.
http://image55.webshots.com/555/8/13...9XXBvje_fs.jpg