So, we just finished up the season yesterday- I ended up taking third overall in Open class (we do driver's classes, as we don't have enough folks to run by car class).
I'm pretty happy with how I did, although I think the PAX doesn't really favor the FiST in STH. That being said, I was really happy with my raw times, as I could usually beat up on 'real sports cars' with decent drivers. I finally beat my nemesis, who I have been chasing for three years now.
The thing I am going to look at most for next year is
tires- the Rivals just don't get warm enough on our small courses, and with our relatively cool ambient temps. I don't know if I can fit the new 225/50R15 A052s under my wheel wells, but it would be really awesome to be able to.