Actually, the PC7 will auto adjust the offset as you ride. You can click this feature on/off using the SRM software (might be able to do it in the PC7 itself but I haven't played with that).

Here's a vid of what I'm asking about:

https://www.bikeforums.net/*****************IuNU

My guess is there's a slight movement in the spline interface during the front/back loading that's putting a very small load on the spider and changing the offset. Was wondering if anyone with the SRM track unit noticed anything similar.