You want it very close to center, but just off center a little bit to get the optimum sound and resonance from your drum. If you measure and beat a skin exactly dead center, it is not as nice a sound.
Romshot,I think you are right.Iasked my drummer.avery fine grad from a top music school and he said no to the center also.It is a "node" as he called it. It is a dead spot due to low frequencys canceling each other out.