Great idea cutting away the old suction cup to make an attachment point! Neodymium magnets are no joke, they're SO strong. I have some frag racks that use them and was very surprised how strong those little things are. My outer ones have a felt pad to protect from scratching glass. I would definitely recommend placing the inside part manually, then putting the outside magnet against the glass 8-10 inches away and sliding it in place. Once they're stuck, sliding them around together may cause scratches
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