Posting Peter's FSS measurements from today with common gain changes.  This is in conjunction with the fast gain changes from yesterday.

Impressions
We are able to reach 500 kHz UGF with Common Gain = 26 dB, getting closer to the top of the phase bubble.
If we turn down the common gain too much, the EOM and PZT paths start to peak at 100 kHz.

I also attached the PC and Fast monitors during the time of Peter's measurements (5:00-7:30am PDT).  If you look closely you can see when Peter adjusts the common gain on the PC monitor, which according to the schematic is 1/10 of the actual PC output.  It seems that  there was no real difference in the PC monitor between the times of high and low gain.

Sheila and I looked at the PC monitor at a time when the IMC gain was increased such that the UGF was 100 kHz, and there was really no difference from a time during lower gain.

It doesn't seem like EOM saturations are causing locklosses in the IMC.