In the absence of a dedicated discussion for GPS IMU...

We have a GPS IMU (v1.0) freestanding (no gimbal) and we are communicating with it no problems over serial to our processor.
The detail in the data sheet is missing the fine detail though. Is there any further documents I can access above those on the download page?

Project is to calculate relative XYZ linear displacement in metres from a home position using the onboard IMU sensors with the best accuracy possible.

Although data sheet does say ground referenced frames are not inertial, does the AHRS frame augment with the GNSS position? Can GNSS be switched off if it is used?
AHRS_STATUS always reads as zeros. Is there a function not being initiated? - no detail.

Would I be better to set the DYNAMIC_MODEL function to something different, and what dynamics are the options changing?

CALIB_MODE what is the difference between simple and precision?
Any feedback is appreciated.