Porthole Pinhole

I make my own pinhole cameras and built a new 5" x 4" camera, and when I developed the films realised I had made the shutter a little thick so it appeared in the shot. My son pointed out it looked like a porthole, so I now have a normal shutter for most subjects and keep the pinhole for trips to the coast. I have contact printed on to resin coated paper in an old frame which adds a slightly irregular border.