I've been using a Super Graphic and a Cambo 45N with a Calumet reflex finder. The finder doesn't mate up to the GG holder on the Graphic, but it is simple enough to swap in the GG holder from the Cambo which easily locks on the Graphic G back. I just bought a Wista VX and hoped to use the reflex finder on it, but I've found that International backs speak in dialects. The spring bars of the Cambo GG frame are spaced too far apart to lock on to the pins on the VX back. The viewer itself will fit into the VX's GG frame, but there is no way to lock it on.
Wista makes a reflex viewer but it's expensive and I'd rather have a singler viewer that I can use with all of my cameras. In looking at the picture of the Wista viewer and my camera's back, it isn't clear to me how the viewer attachs. Can anyone help me out? Any clever ideas for adapting the Cambo viewer?