As part of my research project this year, i have to use Maxsurf Resistance to test different bow designs. I have to argue the validity of the program itself in regards to comparisons to towing tank data. Although I have searched everywhere, there isn't very much on the validity. The only information I have found is a study on catamarans where towing tank data was compared to results from Maxsurf Resistance and only slight deviations were encountered. If anyone could help that would be great thanks!
MAXSURF Resistance is mostly implementation of well known empirical formulas such as Savitsky planning, Holtrop etc. So any validity of MAXSURF Resistance is the same as the validity of these formulas. You can find references for all the original papers at the end of the manual.
The Slender Body Method has also been presented in several papers whose references are given at the end of the manual.
Note that the empirical formulas only measure certain aspects of hull shape. So changes to bow design may not even be noticed by some formulas.