Magnets

I'm trying to attach the horns with magnets and so far I have 7 rare earth magnets, (http://www.harborfreight.com/10-piece-rare-earth-magnets-67488.html) on both side of the horn and it still comes off when I shake it really hard or when the face goes down (like a nod) really fast. I hope he won't be flinging himself around like that but I don't want it to fly off and hurt someone - I'd rather just be extra careful on this.

Are there different magnets I could use? Do I need a lot more? Thanks for the input!