I have finished the bulk of the restoration. I also made a mohogany adapter board for Shen Hao lensboards.
I finally decided to adapt the back to a modern film holder by reducing the light trap ridge on the back only where it touched the film holder. It turns out that the ridge is really a strip of wood inlaid into a groove on the back. Unfortunately that groove is in the wrong place to mate with the ridge on the film holder. So, I cut a new groove to receive the ridge on the film holder. Were I ever to find a plate holder and get motivated to make plates, I would only need to inlay a new strip of wood in the old groove to use the back.
Testing with a flashlight in a dark room and after making small adjustments, the film holder lays flat against the back without any light leak.
I took the camera down the street to Lincoln Road Mall in Miami Beach and exposed my first 8x10 film. There are no light leaks visible on the film in spite of the Floridian sun and the focus is perfect. Inspite of the slightly smaller dimensions of the modern film holder, the film holder fits well centered and maintains its alignment even with landscape orientation of the back.