I actuate on ETMY for YARM and ETMX for XARM. For now I did adaptive filtering for both arms at the same time. I used the same parameters for xarm as for yarm.
I've notched 16 Hz resonance because it has high Q and I need to think more how to subtract it using FIR filter or apply IIR.
I'll try MC stabilazation method.
Adaptive filtering was applied to MC and X,Y arms at the same time. I used a very aggressive (8 order) butterworth filter at 6 Hz as an AI filter for MC not to inject noise to ARMS as was done before
Mu for MC was 0.2, downsample = 16, delay = 1. I was able to subtract 1 Hz. Stack subraction is not that good as for arms but this is because I used only one seismometer for MC that is under the BS. I might install accelerometers under MC2.
EDIT, JCD, 18Feb2013: Den remembers using mu for the arms in the range of 0.01 to 0.1, although using 0.1 will give extra noise. He said he usually starts with something small, then ramps it up to 0.04, and after it has converged brings it back down to 0.01.