The simple truth is that Froude's law doesn't predict the maximum boat speed for lightweight boats with slender hulls. It is therefor nonsense to continue using that law in a fashion that is was never intended to be used.

Froude's law only correlates a rise in drag (wave making) to a specific speed at which the bow wave and stern wave length equal hull length, nothing more. In Heavy boats this wave system is so big that it prevents the boat from going faster. With ligtweight boats with slender hulls is only results in a bumb in the drag plot or an increase in overall drag.

Wouter