Don't be sorry Darryl, I understand what you are saying but we are not talking "missile science" here as I think (without checking google) the weapons you're are talking about are trying to create a "cushion" of air around the submerged projectile so the hydro drag does not exist and the missiles can travel mach 2 under water.
This science has been worked on by the Russians for two decades and they "may or may not" have it.
Like the scram jet engine it might finally come to fruition but not in an obvious way for the beach cat back yard.
So a truly erroneous avenue for what I am doing which is simply setting up a beach cat that planes easily and is predictable sailing above 20 knots.
In that area, as I suggest to Wouter I think a planing hull will go faster , easier than a submerged, wave piercing hull. I think that because I think the planing hull wil have less drag than the semi-submerged hull.
I am happy to be wrong about that and I will provide results here.

I spent a lot of time around science when working in the Auckland Museum. What I observed was that science bends and scientists are often have to back track. When they do they cover their butts by pretending they really knew what the problem was all along and just had to find some "empirical proof".
Science has its drawbacks as sometimes it is about what you don't know you don't know like Einstein not believing in the expanding universe theory and fighting until he died against it even the genius can be wrong.

You never got back to me about the foiled rudders by the way.