Here's an effective and safe filter-mount solution that won't mar or disfigure the camera's lens surround.
Do use 52mm filters, but be aware that at the full wide-angle 28mm setting, the 52mm filter will cause vignetting. This problem 'goes away' with a lens setting beyond 35mm or so. How to attach that filter: Buy a 55>52mm step-down ring. Today, most camera shops will not have this in stock, but can order it for you. It should cost less than $15.00. Then file/sand/grind off its 55mm threads, to create a flat 'back' surface. Carefully Gorilla-glue it to the outside of the stock Canon lens hood, and pay attention to it's 'concentric' alignment, to minimize the amount of vignetting you will get. Once the adhesive sets up, consider painting (flat black preferred) the bright-aluminum 'ring' on the inside of the lens hood that will now face the lens. Unpainted, this might cause unwanted reflections in your images. The included image shows this shiny 'ring' before I coated it with a black permanent marking pen. The red dot on the lens hood is an alignment aid I added, to ease the mounting of the hood.
Final steps: Thoroughly wash and dry the step-down ring's 52mm threads of any aluminum dust. At this point, a light application of lubricant via Q-tip to the threads may be helpful, then screw on your filter(s), install the filter-lens hood assembly to the camera and enjoy a protected lens plus the other advantages of the filters you like to use.
Do note: There is not a lot of finger-room between the 52mm filter and the lens hood. This is a minor problem for me, since I have slim fingers. If you've got big fingers, consider this before starting this project.
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