I'm shopping for a 718 Cayman and because I live in Boston I need to resolve the winter tire issue. I'd like to go for the 20" Carrera Sports Wheels. It appears however that there are no winter tires that fit these wheels. It is unfortunate given that winter tires are available for the same wheels on the 911. I don't know much about tires/wheels size but can anyone tell me if would be able to fit other winter tires for these wheels or should I just give up altogether and get 19" instead (winter tires are available for 19"). Thanks!