Victor's post (gogopix) in another thread (tele lenses) about his converted Telyt-R 1:6.8/400mm made me think and after some thought I ordered the R-to-K mount from Leitax.
Though swapping the mount went quite smooth, there were a few things for consideration, this is what I sent to Leitax:
1. The aperture ring got a very lose fit after the conversion, because there is too much play between the lens housing and the mount (bayonet).
Basically it 'rattles' so to speak.
2. More concerning is that in particular the long screws don't get enough thread windings.
It is as if they're just too short now, which could mean that the holes in the mount are not deep enough.
To some extent this is true for the short screws as well.
Of course it could be just this particular mount for this particular lens, but all-in-all I'm quite pleased with the result
Pentax K5 + Leitax mount + Leica APO-Macro-Elmarit-R 1:2.8/100mm