Randy, thanks for your feedback and for the update!
I just had a look at a Dropix and the IMUs are about 1.6cm apart, on the Pixracer it should be around 8mm.
You write that:
In most vehicles which have all their sensors (IMU, GPS, optical flow, etc) within 15cm of each other, it is unlikely that providing the offsets will provide a noticeable performance improvement
But, since it compensates the position estimate setting the offsets should help for RTK applications even if the sensors are within 15cm of each other. For sure this only makes sense if hotshoe trigger feedback is used and if the camera sensor position is compensated as well:
Looking forward to testing it!