I used the rejected light from the PBS after the motorized half-wave plate between PMC and IMC injection path (used for input power control to IMC) to measure the transmission of PR2 candidates. These candidates were picked from QIL (QIL/2696). Unfortunately, I don't think either of these mirrors can be used for PR2.
If I remember correctly, we are looking for a 2" flat mirror with a transmission of the order of 1000 ppm. The current PR2 is supposed to have less than 100 ppm transmission which would not leave enough light for LO path.
I've kept the transmission testing setup intact on the PSL table, I'll test existing PR2 and another optic (which is 0.5" thick unfortunately) tomorrow.