I currently play the Pro Kennex KI 5(new version). I switched to this racket from the K Blade 98, becuase that racket was making my arm very sore. Now that I am playing the KI 5 no more arm soreness, but my shoulder feels sore after a few sets. Is it possible that I am just not used to the added static weight of the KI 5 ? Thank you for your replies.