Current induced by magnet: maximize change in flux wrt time?

I'm messing around with Faraday's Law of Induction, and I will be using two magnets attached either side to a small bar inside two coils of copper wire, which I spin to induce a current. The design is basically this:

http://ift.tt/1J3r46I



My question is, what shape...



Current induced by magnet: maximize change in flux wrt time?

Current induced by magnet: maximize change in flux wrt time?