I made these because I don't lie tieing my shoes in the morning if anything I leave them tied and slip in and out of them. These are designed with a curve so they lay nicely against your foot. I print them at 50% infill for strength and at the medium quality setting for me that is 0.20 layer hight. I use three magnets on each side for max strength that is a total of six per foot and 12 total. As far as I know, these do not set off metal detectors, I have gone through one wearing them and it did not set it off.
I use 10x5mm Neodymium Magnet you can get 100 for $26.99 on eBay shipped from inside the US.