Thanks for this, mate..
My MTO is the older than yours (and heavier) model, with 1kg of glass in corrector system. It is coated, though, but the glass is still yellowish in appearance and visibly darker, so absorption is there.
http://forum.mflenses.com/userpix/20...O1000A_3_1.jpg
This one below (Rubinar) is much lighter, but also it has significantly better resolution, especially at corners, so I really want to sort it out.
The glue on
retaining ring is still resisting..
http://www.dvdtechcameras.com/manual.../rub1000/1.jpg
The springy compression ring is good idea - I will have it made of plastic (PVC) so I will have 3-point mirror suspension at the edge (with thin pieces of foil for laser printer between mirror and shoulder deeper in the tube) to avoid mirror deformation.