Previous experimental data for the wave profiles behind a series of transom-stern ship models has been re-analyzed in this paper. Convenient and accurate regression formulas for the ventilation of the stern and the length of the transom hollow are provided here. Predictions of the wave resistance and, hence, the total resistance can now be improved by using this approach, together with the traditional thin-ship formulation for resistance. However, the accuracy of these predictions is improved further if one also considers that there must be a minimal effective hollow length based on the flow behind the well-known backward-facing step. These theories, together with the use of form factors, are applied to a series of fourteen high-speed monohull vessels. It is shown that these methods provide a high degree of predictive accuracy.