With the optical levers now well calibrated, we re-assessed the benefits/drawbacks of blending low on Stage 1 Z.  In the plot attached, ETMX Stage 1 Z was in high blend (T750), while all others were in low blend mode. Data was taken this morning from 3am to 4am PT.

- The first plot attached shows that the ETMX optical lever pitch motion is four times higher than the other test masses (second line, third row). This vertical to pitch coupling justify the need for blending low on Stage 1 Z.

- The Yaw motion (second line, third row) shows that the low blends on Stage 1 Z amplify the Yaw motion by a factor of two, through the "Z to RZ coupling" problem that we are trying to solve.

- Just for info, the second attachment shows the Pitch to Pitch transfer functions (second line, second row), from top to bottom mass. ETMX is pretty clean in this configuration as the picth modes are well excited by the Stage 1 vertical motion.