Some screen shots of the rays through the 90mm periscop.
The rays are from a point at 5 metre.
At f/40 and 40 degrees ( near edge of 4 x 5) the COC ( spherical + chromatic) was about 200 micrometre. Not too bad?
The biggest problem was that the focal plane moves as the aperture changes.
F/40 > F/11 it moved from 98mm to 88mm.
The second shot is at f/11 and 26 degrees to simulate the lens on 6 x7 with a practical aperture.
With best focus on the axis, the COC at 26 degrees is about 500 micrometer as shown. No good at all, I think