Can I just ask?
From what I read, you already have the rims.
What size/width/offset are they?
Basically, yes.. you need the same rolling diameter all the way around.
Im running 205/45/16 on an 8 inch rim.
Stretch means less sidewall flex..
sidewall flex is VERY scary through the twisties..
Also, caster (spelling?).. try increasing caster so as the steering wheel straightens up easier during oversteer.
The rest is all up to you.. It depends how you drive. See if you over/under steer and then adjust strut/sway bars and height/damper rates according to what your experiencing, what you like and what you dont like..
It takes a while to get that sweet spot but once you got it.. gosh its awesome!