I also had and liked the magnet bra. I did wax the area twice with Collinite insulator wax (the stuff is supposed to be tough and lasts 5 months out in the elements). I was kind of lazy and left it on for 4-6 months, and thru many car washes.

Was rather surprised to find there was just some faint smudge type marks where it appeared a little water had gotten under and kind of left a water mark.

I wiped it with damp rag (yeah I know not a good idea), and most of it came off. Waxed with Insulator wax again and it returned to 100% normal, no paint color difference or line where it stopped.
Insulator wax has NO abrasives at all, so it didn't "polish" off the marks.

Now mine was NOT out in the sun a lot, which may have something to do with it.

Or maybe it was the Collinite wax, or a combo. But I think the Insulator wax was a good part of the success.

But I loved the magnet bra because it was so low maintenance.

HOWEVER, it does DENT very easy! You have to store it very carefully with no debris under it or it will end up with permanent upward dimples.

Obviously the clear 3M bra like mav has takes care of all these problems, so it's a great choice too.

The magnet bra was only $60, so it's not a huge expense if you don't like it or it gets damaged.

I forgot to put the edging on one time, then went on the highway and it flew off! it was thrashed from the road debris and skidding along the road, had dents all over...had to buy a new one.
BTW I have a brand new edge trim if anybody needs it.