Eep, good luck! I had similar issues with my magnets, but only on one side. One dagger stayed on pretty well, but the other kept falling off when I moved. >_< (I also cheated and made the "Carta's Left/Right Hand" daggers because they are a simpler shape. I also figured that if I was cosplaying Romanced Isabela, it would be later in the timeline so she could have different daggers. :P)
I actually made three necklaces for Izzy... the coin one underneath, the collar over that, and then the snake necklace on top of that. The collar laced up the back like a corset, and the snakes attached in front. It would have been easier to put on and take off if it was one piece, though.