The attached dtt screenshot shows the coherences of MICH and SRCL feedforward with the DCPD sum.

Note in particular the high coherence with SRCL FF between 2 and 5 Hz. In fact, most of the rms SRCL FF drive comes from below 5 Hz.

The attached dataviewer screenshot shows timeseries trends of the DCPD sum (below) and the FF signals (above) during lock acquisition. One can see that turning on the feedforward appears to increase the DCPD sum rms.

Also attached are TFs of the foton filters used for the feedforward.