I ran -3.5 (F) and -1.5 (R) last monday at NJMP. I'm also -.1 Toe (Front) and 0.05 Toe (R). 275/35x18 No stability issues and much better turn in. 295/30x18 (Rear) - R6s
Auto Cross I run -4.5 (Front) -2.0 (Rear) with same Toe as above and 285/30x18 (Front) and 315/30X18 (Rear) A6s.
Notice the outside front tire is flat on the ground during an aggressive turn in.