I have been looking to purchase a set of Carerra S II wheels off of an 09. A wheel dealer has a set off a C4S. He told me the fronts are the same and the rears will also fit correctly other than the wheel will sit out one inch further, the same as a GT3 setup. I would appreciate any imput, verification or advice. I have an 06 C2S. Cheers.

 

almost correct. the rear wheels of a c4s will sit out 17mm farther out than the stock c2s wheels. thats about 2/3"

and yes they will work on your c2s but have a more aggressive look (desired)

if you want to see what it will look like, look at a 997 GT3, it will look about the same

 

Actually a 997 GT3 is a narrow body car just like a Carrera or Carrera S.

The GT3 RS is the wide body coar just like the Turbo and C4/C4S.

 

I suspect you need to consider the risk of tire rubbing if you ever lower the car. Having done so, with 5mm spacers (and no problem) I imagine 17mm would be getting pretty close. Particularly if you're running 305's.
Others on this forum would know for sure.