What do you mean by PR2, PR3 flipping? They are (supposed to be) flat mirrors, so obviously they should be installed correctly, but they won't change the mode matching in a huge way if they're backwards, right?
We see some ghost beam spots at POP. This may come from the back of PR2 and PR3. Also, they may change mode matching because of thermal lensing, mirror deformation, and other unexpected reasons. I thought we should check every mirrors in PRC, if PRM is not flipped.
We are going to check PRM just because we spent so much time for the PRC problem, and still don't have the solution or evidence.
PRM flipping is kind of the only idea for the root of all evil -- terrible beam shape, low PR gain, unstable PRMI lock.
So, I want to check with my eye during the stay.
I don't think we have to redo magnet gluing. It's okay to leave them on HR side.