After installing the new filters on ETMY suspension, I took an open loop gain transfer function of the top mass in the longitudinal degree of freedom, with the loop closed, and compared the measurements against the model.

The first pdf attached shows the measurement in blue, and the model in green. Except for the first pitch mode, at around 0.5/0.6Hz, they match really well.

The second pdf attached shows the open loop gain transfer function for different damping configurations that have been used during HIFO-Y commissioning. The old filters mentionned are refering to the one Jeff K. designed to reduce sensor noise contribution to test mass displacement added to the extra boost at .43Hz and .99Hz

The new filters are clearly more stable, providing the same damping at the lowest longitudinal mode than the previous filters with a phase margin of 36 @ 3.54Hz.