Ok.. lets see if you can back up your statements. The first place to start is to look at the stiffness. Since you say one is more stiff than the other.
What is the stiffness of each boat?
I say that one is more stiff than the other? You have any doubt?
The stifness of a boat is directly related with the boat displacement and the sail area the boat can carry (SA/D). You can see that big difference yourself. The data on both boats is on the net.
I appreciate your effort to understand and relate seaworthiness and stability with mathematic formulas but on your efforts you start from the wrong basis:
Instead of assuming that boat design did not evolve in the last 50 years, as well as the way seaworthiness is obtained in new designs, and try to prove that old designs are the only way to obtain a seaworthy boat you should try to understand how modern NA have obtained seaworthy boats with different design criteria than the one that was used 50 years ago.
There are several ways of obtaining a seaworthy boat and mass and a relatively high CG is one of them, unfortunately one that gives slow sailboats. There are other ways, like the ones (based on static and dynamic stability) that permits a beamy low mass boat with a very deep CG, like a class40 racer, to be not only fast but very seaworthy and that's a fact.
You should try to understand how that massif seaworthiness (that is a fact) is obtained in a boat that contradicts the ways it was obtained 50 years ago instead of, against the reality, assuming that boat cannot be seaworthy because it is not designed accordingly with the principles that 50 years ago were used to design seaworthy boats.