Since pinholes have infinite depth of field, the lens will be in focus as well as everything else, unless the lens is pretty much immediately in front of the pinhole. Any dust or scratches on the lens will be recorded by the camera. I've used this principle to conduct short (20 minute) pinhole-on-a-stick demonstrations to elementary school kids. We make a pinhole and mount it on a piece of mat board. I have a set of bug-eye viewing cones which have a lens about 1 1/4 inches from the narrow part of the cone. I ask the kids to look through the cone with just their eyes. They see the world multiplied by the facets of the bug-eye lens. Then I have them look through the pinhole (mounted to a piece of mat board) and through the bug-eye cone at the same time. Then they can read the word. This proves two scientific principles at once: 1) human eyes have lens in them which are unable to focus close enough to read the scratched word on the lens; and 2) the pinhole is an image-forming device with infinite depth of field which takes the light coming through the lens and creates a new image and projects it back to the human eye. Kids are fascinated by this. And your idea to mount the lens on a cardstock cylinder will be a fun experiment. Try different focal lengths.