To decide whether the end mirror should be circular up to the spoke "full ring" or whether there should be a flatter interface "cut ring", I simulated both in COMSOL with 2 mode corrections, the 20 + 02 HG mode and the 11 HG mode.
In summary, the rounder optic seems to perform a bit better when considering the deformation per joint stress, deformation per force applied, and eigenfrequency. The more circular mirror also has a cleaner edge and a larger reflecting surface. If Knight Optical can make them, I think we should get a circular mirror.
Full ring:
20+02,60 N:
9 MPa Max stress
6.3 mD adjustment
0.7 mD/MPa
0.1 mD/N
11, 25 N:
4.3 MPa Max stress
9.4 mD adjustment
2.2 mD/MPa
0.37 mD/N
Resonance: 3943 kHz
Cut ring:
20+02, 60 N:
8 MPa Max stress
4.2 mD adjustment
0.52 mD/MPa
0.07 mD/N
11, 25 N:
3.6 MPa Max stress
8.6 mD adjustment
2.4 mD/MPa
0.34 mD/N
Resonance: 3878 kHz