I ran Square 285/35/19 GYSC3R and now running 265/35/19 F on 10" wheels and 305/30/19 R on 11" wheels GYSC3R. Just experimenting
285 in F with 305 in R seems to be the combination but not possible with xdrive. 265 on 10" wheels front end grip is not up to the point. Next gonna experiment 275/35/19 and 305/30/19. trying to keep the diameter close to 1%. Some one in FB ran Falken 660 275 and 295 and said xdrive worked flawlessly at track. Someone need to break down what is the tolerance %