[Leica] Using screw to M adaptor ring ? Need Help

[John Coan <jcoan@alumni.duke.edu>]

I recently acquired a used Voigtlaender 15mm screw mount, and purchased
a Voigtlaender adapter ring.  I have a few questions that I hope the
group can help me out with.

1.  The instructions say put the ring on the M body and lock it in, then
screw in the lens.  I always figured I would leave the ring on the lens,
and bayonet the lens on and off like a normal lens.  Any problem with
that?

2.  When screwed all the way in, the focus indicator mark which should
be centered at the top is a few degrees to the left (when looking
down).  Sort of like it is screwed in a little bit too much. Will this
have any practical effect on focus?  I've never owned a screw mount
Leica and do not know how precisely the threads are cut to make the lens
line up perfectly when screwed in tightly. On my combo, the lens isn't
tight unless screwed in a little past the mark.

Thanks in advance for the collective wisdom of the group.

John