Couple have thoughts. PHRF was designed to handicap boats of similar design and size. A 65 foot and 30 foot are not going to correct out. A 35 foot hunter and 30 foot Catalina ok. A Nonsuch 30 and a C&C 30 no.
Each "region" will adjust ratings based in experience over time. Some regions are more diligent some less so .
A Nonsuch will owe time to everyone. I was giving time to Mirage 30's as I recall. Using a blooper will put you in spinacker class and you can not fly a blooper over about 9 knots apparent plus the time to douse and raise the main makes it impossible.
Where we had good success was on long distance races that were not dominated by windward legs. Long enough for competition to make mistakes.
In light air you will struggle . In anything over 20 knots you'll do well as most racers hate to reef and pay the penalty.
Jack Lombard in the Long Island group did some excellent work in developing rating for the Off Sounding Series . I'd get in touch with him I'm sure he can assist.
I did bolt a roller fearler to my Sampson post and delemaded a 6 second credit. The PHRF measurer didn't want to give me the credit as it was not connected but I did point out to hime there was nothing in the rules saying I had ti actually use it.
T