my Leitz focomat Ic enlarger carrier leaves a black edge most of the time without grinding -- not sure if it's an HCB leftover or what.

There is a coda -- it only leaves the edge with R-lenses (and Nikon) but with M lenses it only leaves the edge if I use a 50mm lens or wider -- M cameras use lenses that are not a reverse-telescope design, they are 35 mm (or whatever) because the lens is actually physically that close to the film, so the image must be projected more widely to fill the frame at a wider angle, which with wide angle lenses projects under the edge of the back of the camera frame onto the film.

With my 21 mm Super Angulon lens on my M, the rear element is so close to the film I'm amazed there's room for the shutter -- and the images created by that lens projecting the light so widely onto the film to cover the frame actually touch edges on the film. I've had people tell me my camera was spacing the frames wrong, but no.

Have you considered just drawing the black edge on?