There are lots of references on the interweb and they mostly give me a headache reading them coz I’m not that smart but roughly if the tail (Rudder foil in this case) area multiplied by the distance from the main foil ( i.e. area x distance called volume by convention)is correct for the main foil size, shape etc then an airplane (yacht) can be designed to be stable in pitch. It still requires some adjusting while under way but nothing too drastic. If this were not the case then it would be impossible to fly ordinary airplanes. Interestingly relaxed static stability is good in some cases like fighter aircraft. But in this case fly by wire control systems do the hard graft and the pilot just decides where to point the thing. Computer does the rest. Something like that anyway. Keep up the great work though you are way beyond what I can do.