Calculating Cp shapes on elevation profiles (car etc. with no depth dimension or detail) is very easy.
Actually that is calculating the center of
side area, not Cp. Yes, there is a BIG difference between the Cp contribution of a round nose and a flat vertical tail; that's why it's not a simple process and cannot be measured correctly by simply plotting side area.
And yes, a reasonably sized tail can straighten out a lakester. The best example was Al Tegue's lakester-turned-streamliner where the rear wheel fairings served as VERY large tails. People on the team told me that the car was very aerodynamically stable and would come back in line anytime the traction slipped and it went out. The same thing was reported by another team that I spent some time with this year on a door-slammer that I knew to be unstable in yaw: They added fairly small tails the first time out and the car drifted pretty significantly above 200. This year they put on bigger tails and the can was so solid between 200 and 300 that the driver actually steered it around a little on purpose to make sure he still had traction and wasn't going straight on luck and an airborne front end.
Finding the aerodynamic neutral point can be done with CFD, but modeling anything by the simplest car is time consuming and expensive. Doing it manually is a bit of an art, and I can recommend some good books on the subject.
