I started this season with a non-pealess whistle, made of hard plastic. I was given a Fox 40 whistle with the rubber teeth-guard a few weeks into the season. As of today, I have chewed the rubber to pieces, and cracked the (thinner on the mouth-guard whistle than the regular) plastic part of the whistle you put in your mouth. I want to use the regular Fox 40 because it is more durable (and cheaper), but I am concerned that biting the hard plastic might hurt my teeth. Anyone had any trouble with a chipped tooth?