Switch Blade;
My assumption would be this (based on my 1:10th experience);
If you mount your servo more forward this will affect the ackerman, whilst the vertical postion would affect bump steer.
The idea would be is to get the steering links level, as this eliminates bump steer.
With regard to forward sweep, a little forward is good, as when the car is on full lock, the outer link will be straight. I'm not compeletely sure how it affects the ackeman (always get a little confused with that one)... someone else ahould be able to tell you.

HiH
Ed