[Leica] Summarex question

[Simon Pulman-Jones <spulmanjones@lbs.ac.uk>]

I have recently acquired a Summarex 85/1.5 - not expecting much, I have so 
far been pleasantly surprised by its performance wide open.

My question is this - the lens head of the Summarex unscrews behind the 
aperture ring making me wonder whether it can be fitted to one of the 
focusing mounts for the viso - such as the ZOOEP for the 90 Summicron.  I 
can't find mention of this anywhere - does anyone know whether it is 
possible to use the Summarex lens head on a viso?  Focusing at f 1.5 at 
85mm is pretty hit and miss on the M rangefinder - especially at short 
distances - being able to use the viso would make it a lot easier.  I 
imagine that the only way that this would work out is if the thread and 
back focus distance of the Summarex lens head is the same as the 90 
Summicron lens head.

Can anyone tell me about their experience of using the Summarex?  I haven't 
been able to shoot enough yet to work out what I think - for low light, 
close up, it looks as if its performance might be just acceptable - 
yesterday I did some theatre photos - I hope it should perform a bit better 
at fifty feet than at five.  However well or badly it performs, at f 1.5 at 
85mm it performs better than any other Leica rangefinder lens!

Simon,
London.