I managed an hour outside last night and tested the mod on the guide mirror – much better! There is now a ‘sweet spot’ in the middle of the guide image (rather than at one edge) and I think the image as a whole looks generally a bit better. Recall I tilted the guide mirror forward using a washer between the mirror mount and the frame. I should get in touch with Francois I think…
I know that early versions had three degrees of freedom on the guide mirror (two tilt and back-and-forth). The reduction to one with the piston design has thrown some of the ‘baby out with the bathwater’ in my view..
Incidentally – adjusting the main mirror angle still has the same effect as described in this thread (move image across sensor and change its height) – my tweaking the grating has made no substantive difference.