To prepare for controlling DARM using ETMY, I copied the changes the Keita has made to damping and L2P decoupling for ETMX (alog 16968) to ETMY .  The attached screen shot shows the transfer function from an length excitation on L1 to the pitch optical lever, red is before copying from ETMX and green is after.  The lower plot shows the op lev spectrum durring the excitation.  

I also checked the L2P and L2Y on L2,  this was done simply by putting an offset onto the length drive which used about half the DAC range, and looking at the impulse response using the oplev.  The arrangement of filters that was already engaged seems to do well for L2P, it reduces the impulse response by more than a factor of 10 compared to having no L2P decoupling on.  for Yaw there was no difference really between the filter I found engaged and having nothing on, for the time being I'm leaving it on although it could be turned off.