Measured free swing PRM-ITMY length was 230 nm RMS.
MI differential length was 85 nm RMS(elog #8248). This tells you that PR2, PR3 are not so noisy compared with usual suspensions.

Openloop transfer function:
  OLTF of PRM-ITMY cavity lock using REFL55_Q_ERR as error signal and PRM as actuator is below.
  UGF ~ 120 Hz, phase margin ~ 50 deg.
  Somehow, phase delay was 460 usec, which is smaller than the empirical value 550 usec.



PRM-ITMY length spectra:
  Below. Calibration was done using calibrated REFL55_Q_ERR and actuator response(elog #8255).