I have not seen any recent examples of MF mount matting of 35mm.  I recall a very impressive show back in the early 1960's, where someone (I forgot the name) had hand-cut mattes and mounted 35mm pairs in the MF frames.  I remember that he also had a home-made dissolve unit for the two projectors.   While some of the images were centered, others were not (intentionally offset).  He did all sorts of things, including putting multiple realist images on one MF slide, masking some images to irregular shapes, and intermixing dual camera full 24 x 36 frames with the smaller Realist images, which the MF area also permitted.  An audio tape track that accompanied it included narration as well as music, and in one instance there was a brief dialog between two people, wherein he switched back and forth between images as each person spoke.  Their images were presented alternately in the vertical 35mm format, one person on the left half and the other on the right half of the other MF mount.  At the end of the conversation, both were shown together on a third slide.  At the end of the show, the last slide was a full MF stereo image (a scenic) that he had shot with a single MF camera on a slide bar.  This was so long ago, that I do not recall if I saw this at a PSA event or some other show.  Does anyone else remember it?

 

JR