id double check the weights clifford. you might be weighing down your sports car for no reason.

I bought my tires 6 months before go TT, 305 rear and 265 in the front. I didn't notice much difference from stock, I was lowered Tiens at the time. I would get spacers, 15mm all around, you can go 20s in the front with no problem. The only thing with going with a wider lower profile tire is that you will need camber arms and toe bolts in the rear. Once I went to coil overs I had to add front upper arms to get the alignment back into oem specs. If you keep it stock height you may be okay but if you drop on Swifts or coil overs it's crap shoot unless you are okay with running a lot camber and replacing tires frequently.