In order to better quantify the yaw motion of the PR suspended mirror I made the optical lever reflected beam imping on a ruler put at a distance of about 88 cm from the mirror.(See attached picture 1)

I started from one side of the picomotor range (left column of the second attached picture) and I kept turing the screw as far as I was able to see a beam movements on the ruler. 

I had to stop well before that the end of the range of the picomotor (right column of the second attached picture) since the beam was not moving anymore (and the mirror was oscillating a lot)

Even if it difficult to clearly see it, I think that the intermiate mass was touching the magnet holder plate preventing a further motion.

The total motion of the beam on the ruler is about 1.5 cm which corresponds to 8.5e-3 rad.