I'm getting caught up after a hiatus...
Just to add my .02 worth.
Doug is spot on in every respect.
If I can make a recommendation for the future. In GS, you can run a DOT legal competition tire.
The manufacturers build in a "fudge" factor to the tire design. Smoe, like the BFG and the Hoosier build in 1/2 degree of negative camber into the tire (that's why they are hard to stand up).
They also play with the sizes to allow for greater competition.
For example, I ran the Toyo Proxes RA1 on the stock wheel. A 235/35
R17 which is roughly the same height as the stock wheel/tire combination.
Hoosier (my preference) makes a 225/40R17 that is actually closer to a 235 in width (design "fudge"), but much stickier than the Toyo.
The wider tire gives you quicker turn in and response - especially in high speed sweepers and reduces understeer.
Also, they will NOT
Good luck with your season!