am I to understand PHRF correctly in that it varies by "region" and there appear to be different "scratch boats" in different PHRF areas?

I looked up my C24 rating (from 74 to 90) and it varies depending on which PHRF zone I'm using.


To be anywhere close to bridging the mono/multi conversion gap, would you have to practically sail all boats a nautical mile up and down in various wind/sea states (to get baseline information for future formula development)?

And how the heck would you develop formula(s) for semi- and full- foiling boats?