Just my two cents, so please don't get upset or take this the wrong way.
Racing soft's makes this really unrealistic. Since these S2000's are suppose to be street tuned, no S2000 has racing slicks on driving around the street. Also, this would make for a great long race series. One race every week, for a few weeks. Would help drivers practice the upcoming course for the week, and get a little tuning time in before then. Just in the past, I have seen races like this fall apart since your trying to get x amount of races in. While some people might leave for whatever reason. In my opinion, it makes more sense breaking this down into a few weeks, and making it like a 15 lap battle per say or whatever you wish.
I don't mean to sound so dictating, just my two cents like I stated at the start. Good Luck!