Just one note here, dunno if it improves the art or not: the power from the hammer comes from the increased velocity of holding the end of the handle. The second hand holding closer to the middle may increase control but will decrease overall power.
Hmm, that negates the energy created by centrifugal motion, but, you know, if it works. I get that art isn't necessarily instructive nor physically possible in the real world. I'm just letting my fizzicks nerd out for a play. Time to put that back in the bottle.