Andrew - make sure to have a stopper knot on your traveler line so you're not relying on the plastic stops on the beam...the stopper knot will hit the cleat fairlead and stop the traveler. The stoppers don't really take much of a joke.
Thanks Jake. i have corrected that by simply connecting the traveler and main sheet so it can't go full travel. but great idea for anyone who doesn't connect their lines.
ps mystere's have no plastic stoppers.. just the beam bolt heads, perfect for shearing!