I was fooling around with some things at the track, and one was using the Tamiya short ball stud on the rear of the upper arm. Most of the time I run the standard size ball stud, or even use shims under the ball stud to raise the height. The short ball stud looks to be 1mm shorter than standard.
I was using my Harbor Hobbies TCS foam setup from last year to prepare for the upcoming TCS races. Shortening the rear upper ball stud took caster out from this setup, which made the car want to slide instead of traction roll...exactly the same thing it does with rubber tires. Just shortening this mounting point may not have 100% the same results for everybody, since there are some specific things I'm doing with the kingpin spacing as well that probably affect caster angle. At the same time, getting a little caster out of the car can help if you pick up a traction roll.