diafine - http://www.dunnamphoto.com/diafine_developer.htm

Looking at your first post and what your stated requirements are I believe a 35mm rangefinder is your best bet.

Any handling/focusing/mirror slap/etc problems you are having with your F65 will be magnified by moving to a Medium Format SLR like a Mamiya Pro 645 or similar system.

If your goal was to take Michael Kenna style night photos (long exposure's) I would be very inclined to recommend a larger MF system camera, but for documentary/street style shooting you are likely to find the extra size/complexity/etc to impede your ability to "get the shot".