This is why I bought mine. Very useful.
I had the same problem with chipping and breaking with my smaller magnets. I recommend you wrap each one in single layer of painters tape. This will help the breaking problem, but caution should still be taken, They hurt like the dickens when you get caught in the middle of these with the meat side of your fingers/arms. Blood blisters will occur. and if you are alone, your only real option is to PULL it off OUCH!.
Also, when in use on your armour, keep the armour far away from other items being held with magnets or magnetic items, as they will suddely find there way to connection and mess up your gluing handiwork.
Good luck.