Thats A LOT of space in my eyes as well. Of course it could be the angle of the picture but overall it looks like 12's "should" fit with a maybe a 305 tire. I guess I won't know until I try..
Is there anyway you can take a couple of up close pictures of the rear wheel clearance? 20x11 (+53) is what I ran on my S197 with no issues...there was even room to run 5mm spacers (with my 295 tires). I was hoping that since this car has IRS now, they should tuck inward allowing a little wider...