Custom rubber stamp and a lesson in loose mirror malfunction

This video may interest anyone whose laser is producing unwanted abrasions on the far left and right edges of their projects. This is longer than I prefer to post but I thought it would help other people to see not only the physical affects of a slightly loose mirror on a project but also the miscalculations we made on the path to figuring out what was causing the lace-like holes in the rubber on the horizontal edges of the rubber. My husband thinks that this problem wouldn’t have been as obvious if we had been using a different material but of course we can’t be sure what you’d see using wood or acrylic or another material. I hope this helps someone.