For the PRM, it is also a mostly translation effect as calculated at the PRC waist position (ITM face).
I made another estimation assuming that PRCL RIN is caused by translation of the cavity axis:
In order to get translation to RIN, we need to know the offset of the input beam from the cavity axis...
This should be possible to calibrate by putting a pitch and yaw excitation lines into the PRM and measuring the RIN.
See secret document from Koji.