We did two rounds of MICH to DARM feedforward tonight by actuating on the ETMs as opposed to the ITMs.

We did the usual measure MICH_OUT to DARM_IN1 with FF off, then measured MICHFF to DARM_IN1, divide them and fit a zpk to them (via Lee's iirrational).  That gave us the result in PDF 1, and the orange lines in PNG 1.  This filter is named "Nov5" in the MICHFF filter module.
The coherence was largely reduced, to be sure, but the performance was mediocre between 20 and 35 Hz due to bad phasing.  

So we iterated on the fit using Jenne's convenient feedforward paper.  We retrieved the current filter in the MICHFF filter module using my filterModuleStateExtractor (call it alpha), and found beta = 1 - (DARM IN / MICH OUT)/[alpha * (DARM IN / MICHFF)], the iterative filter TF.  This gave us the fit in PDF 2, and is the red line in PNG 1.  This filter was implemented as "Nov5b" in the MICHFF filter module.
The coherence was reduced further in the 20 - 35 Hz band.  

This process was useful because the first round of the feedforward reduced the noise sufficiently to give a clean TF of the high-Q notches we see around 18 and 25 Hz.  I figure MICH to SRCL to DARM accounts for most of the remaining coherence, we haven't redone the SRCL to DARM feedforward to the ETMs.
The change from ITM to ETM actuation and MICHFF FM engagement is updated in LOWNOISE_LENGTH_CONTROL.

The templates for the MICH FF measurements are:
/opt/rtcds/userapps/release/lsc/h1/scripts/feedforward/MICH_to_DARM_excitation.xml
/opt/rtcds/userapps/release/lsc/h1/scripts/feedforward/MICHFF_to_DARM_excitation.xml

The results for the DARM IN1/MICH OUT and DARM IN1/MICHFF are actively read by the script in /ligo/home/craig.cahillane/Git/Feedforward/MICH2DARMfeedforward.ipynb.