My Turbo Optima runs pretty solid with double sided tape and tie wrap mounted servo.
http://vimeo.com/91021555
The key is to use tape with a thin "core" I think. Some double sided tape have quite a bit of foam between the sticky layers, and this foam allows flex. Great for reducing vibrations for electronic parts, but lousy for mounting a steering servo.
Also sure that there also isn't too much play on the bell cranks? If these have some play, they can "rock" on the metal posts and this makes the steering sloppy. I used some small shims from 3Racing to reduce play, while still keeping the bell cranks moving smoothly. This reduces play and drag on the moving parts.