secret is to be relaxed. Swing from the shoulder and let the weight of your arm do the work. The more you use your core to accelerate the arm, the harder you hit so remember that you aren't trying to break any bones, just her spirit.
"Both the GTX and GTR models were limited to a top speed of 180kph. However, removing a screw on the back of the instrument cluster, labeled 180kph, meant that the speed limiter was removed."