I still think we (OK, Pete Melvin) could come up with a much more accurate speed prediction program for cats, that relies on the simplest measurements, such as water line length, beam, total weight, either with or without crew, (racing displacemnt) total upwind sail area and downwind sail area.

Unlike all the different Monohull hull shapes, all cat hulls are pretty much 'torpedo' like, that is, they are long and skinny, so the real 'speed' factor is;

How much does it weigh, how much sail are does it have, upwind and down, and how wide is it?

Seems to me someone must smart enough (don't make me call Wouter!) to come up with a simple speed prediction program for cats of all sizes, that could factor in those simple measurements and be much closer than the Portsmouth numbers.