A lot of the SCCA/NASA guys are running 17x11's with 315's at both ends of the car.
FRRAX has a great write up on the fitment and related consequences--->
http://www.frrax.com/rrforum/index.php?showtopic=2922 Please remember when reading this that these guys are talking about racing applications. On a street car a lot of the wear referenced will take long to show up.
I have never driven a car with that much rubber. I can tell you just adding a set of real one season tires will make a night and day difference with the 275's. I would suggest before going to large by huge wheel and tires get adjustable everything and use it to perfectly center and square the suspension at ride height.
If you have more questions about the consequences of big wheels hit up Paul from CTW (Sponsor on side bar-->>>) he has a lot of knowledge and data to back up how more tire can change balance and grip levels.
-Tim