They don't but only pirrellis in 20" and Goodyear in 19" are available (n rated) unless you want to go sport cup 2's All are way cheaper at tyreleader than anywhere else 4x20"pirrellis for 720 so say 750 with fitting.
At the moment yes, unless you go for mitchelin sport cup 2's off a gt3 and go 305 wide at the back. Brave if you use the car year round. It's rumoured that super sports will be n rated in 20" 991 sizes in the next couple of months though
