Hey your setup is almost the same as my previous WedSports in the rear (i had a 25mm spacer). Dunno how much my car is dropped but i had almost no gap between my rear tire and the fender. I also had -3 camber in the rear and was still rubbing bad on steep driveways.
I think you could run a 275 but it depends on how low your car is and how much camber you are willing to run.
These are the best pics of the rear fitment i could find for you:
This pic was before i got an alignment at -2 camber but its just to show you how a 275 fits on a 10.5in wheel
Hope this helps
