255/35/18 Pirelli Box S (Yes or No?)

[thstone]

^^ What BYprodriver said.

Spec Boxster's are probably not the best comparison. While they do run 255/40/17 rear, the cars are purposefully set up for less understeer/more oversteer to acheive as close to a neutral handling car as can be acheived. Without the requisite driving experience, this setup can feel darty on the front end and loose on the rear end. This is generally not ideal handling for a street car.