You are right. We should change or rotate the mirror mount.
Actually when Suresh and I were putting the mirror we rotated the mount by 90 deg such that the fat side of the mount is at left had side.
It was because the fat side had been clipping the oplev beam when the fat side is at right.
At that moment we were blocking the green beam to only see the faint IR beam with a sensor card, so we haven't checked the green beam.
Anyway the mount is apparently not good for the green beam.
I didn't notice it the other day when I was working on putting in the trans QPD, but do we need to switch the mirror mount for the first turning mirror of the IR trans beam, which the green transmits through to go into the cavity? It seems like we've set ourselves up for potential clipping.