My two cents regarding the Viper tuning guide: i would suggest that the main sheeting tension may be dependent on the cut of the sail, the leach and how open or not it is. Also, does the Viper have the same set up on the mast anti rotater as the Taipan? If so it is referenced to the boom instead of the tramp like the American Blade has it, therefor the adjustments are different for different main sheet settings.