I have a 2005 911 997 c2 and have currently on it c2s 19 inch rims on it with snows on them. Since its not the wider body it fills out the wheel well and fender.
They are
235/35/19
295/35/19

Now the question.

I am going to use these rims as track rims and have purchased the pilot sport cups for these
rims but 305/335/19 for the rears because they weren't avail for in the 295's....the shop says they will be fine and perform well??? Will this size change affect anything? Will it be fine? Also my cars not the wider body?

 

Yes, they will be fine. I'm running 305 now and thinking on switching to 315 next with 245 on the front.