Hi Jolly,
If you took all the presently available US built boardless beach cats in the 16ft, 17ft and 18ft length range and measured their bow heights and then took them out and made them pitchpole using the same sailing technique, you will find that the taller bow height boats are harder to pitchpole than the shorter bow height boats.
The imiginary boat you described with the torpedo hull shape underwater has no pitchpole resistance because there is no reserve bouyancy at the bow. It is the reserve bouyancy, the freeboard, in the forward end of the hull that when pushed underwater makes the center of bouyancy migrate forward in the hull and this creats "restoring moment" which opposes the pitching moment from the sails and stops the boat from "pitchpoling". When the foredeck finally goes underwater, there is no further increase in restoring moment so the boat frequently "pitchpoles".
The craft you have configured with the Torpedo foredeck/hull shape that sails underwater has no additional or further increase in restoring moment as the bow is pushed further underwater. As I understand your configuration, it would pitchpole quite easily.
Think about the modification done to Playstation to improve its "pitchpole characteristic". How was that boat changed? The bows were extended 20ft and made much taller. These changes created more "reserve bouyancy" further forward and resulted in a major increase in restoring moment for Platstation which allowed the boat to be driven harder and faster than the original design.
sailing rules, meet Mr. Bernoulli
Bill,