I did a very quick search and didn't find any other posts, so I putting a plot here comparing the motion of the pre-vent HAM1 TT L4C passive stack motion to the current HAM1 ISI motion. ISI motion is generally 1-3 orders of magnitude better, only with a very narrow window at 15hz where the passive stack barely reached down to the ISI motion, but only for the x dof. Blue, green and brown are the ISI, cyan, pink and black are the passive stack.

Almost done with the st0 feedforward, X,Y,Z and RY are running. Still have to do tilt decoupling (which will improve low frequency motion), vac work at the chamber kept tripping the ISI during my measurements this morning.