I went through it this afternoon after posting, and held the film up to the back to see how it was oriented and how that relates to possible leak areas. I now believe the leak is coming from where the foamed corners of the film carrier meet the closing latch side of the back. I did not replace those corners because they looked OK, but now I will. They may be compressed. I will also try the light inside the camera trick, I haven't tried that yet. Thanks