I'm using the Spigen neo hybrid case and the magnets hold good enough even with tight cornering. I also tested with the Spigen ultra thin also. The magnets hold nicely as well but it shifts a bit more because of the smooth backing.
Cool. My local Dollar Store sells those rubbery (silicone?) dash mat grip pads. Can trim down to size and place it on top of qi charger. Probably not thick enough to interfere with the inductive charging.
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