--Further testing showed that previous magnetometer calibration seemed faulty.  Redid calibration procedure and got the following: (saved in  ~/razor-9dof-ahrs-Release-v1.4.2/Processing/Magnetometer_calibration/output2.txt)
	  #define CALIBRATION__MAGN_USE_EXTENDED true
	  const float magn_ellipsoid_center[3] = {150.519, -45.9270, -79.4291};
	  const float magn_ellipsoid_transform[3][3] = {{0.926888, 0.0181419, 0.0232870}, {0.0181419, 0.979668, 0.0126558}, {0.0232870, 0.0126558, 0.971117}};
Entered this into Razor_AHRS.ino and reprogrammed.
--Mag update improved yaw/heading tracking when board was separated from rover, but still had erroneous results when mounted. Some experimentation showed that the errors seem to be due to the proximity of the IMU to the motors.  When mounted over the left middle motor, 1 cm above the deck, heading tracking was bad (a 90 degree turn of the robot showed little to no change in heading).  However, when the IMU was held at the approximate center of mass of the rover (adjacent to and behind the panoramic camera) and ~4 cm above the deck, heading tracking seemed accurate.  Taking the rover down to the machine shop to see if they can assist with remounting the IMU.