You have to hit it straight on, bang in the middle, otherwise it absorbs a fair chunk of the power.

Its so funny when your out and see all these big daft blokes trying to monopolise the machines, then one smaller guy comes up and shows them up infront of the ladies.

Just like in real life fights, its not how big you are, its all down to technique, although most big people seem to assume otherwise. Its usually the crazy small guy who wins everytime.