CMPS11 Problems

I am having difficulty using the CMPS11 tilt compensating digital compass. The problem is accuracy. It is very repeatable. It is mounted on the front end of a small tracked robot with the motors in the rear. Distance from compass to motors is about 7cm. I perform a calibration cycle in the area where it is to be used. The nearest iron object is about 2m away.

    1. Is is reasonable to take compass readings while rotating?
    2. Should I relocate compass to center of bot (would be closer to motors)?
    3. Should I implement a software angle adjustment scheme.