Yea sounds like youve heat cycled the tires out of their prime. Still way better than all seasons, but to really compete youve gotta have a dedicated autox set that stays in bags between events. I dont do this, yet.
I run my fronts at ~half stiff to help the front dig in. I came from racing my boosted miata so I definitely prefer the handling on the twitchy, oversteer side. Its like a bull ride, going back and forth between taming understeer from over throttle, and oversteer from late breaking, or throttle lift oversteer. Definitely utilize the "string theory". If you start turning while you are still braking, the car will want to rotate. You CAN use this to your advantage.