I know nothing about asphalt racing, thus nothing about the Federal or its characteristics.
By the lack of responses, and lack of clarifying questions, I'm guessing that this question is getting too close to the super duper secret set-up stuff you have to pay for.
Like I said, just a guess.
My left rear American Racer is from the first set I bought. Has over 50 races on it and durometers at 49, but that's not going to help you