I took a look at the YAW angle for the HAM HEPIs associated with PR2 (incorrect by me) (HAM2), SR2 (HAM4), and SR3 (HAM5) based on this previous alog83705. I believe the IPS channel units are in nrad, so the largest yaw angle I see is on HAM2 with 1800 nrad or 1.80 urad, HAM2 and 4 are different by ~ 1.10 urad.
I added on the RESIDUALMON channels at Jims recommendation which directly tells you the error from the reference location.
Here's HAM3, 0.392 urad as seen by HEPI