Are you talking 18" for the 235/265?
A 295 is best on a 10.5" rim, 265 is best on a 9.5" rim. There's no stretching, the opposite actually. You certainly don't want to bulge a R888 or you'll get the "groove of doom"!
Might want to consider the
I run mine like this:
The fronts I run -3.3° camber, rear -1.8°
This is all on my Mcoupe