So, I feel bad that Mark has been in here doing all the heavy lifting! I'm the technical rep for SCHRS in the US and I work with the World Counsel and Technical Committee on a variety of things; data review, areas of concern, changes to class rules, etc.
Mark has done a great job explaining how SCHRS works! I think one word that has been missed however (it was alluded to) is "Corinthian". The point is this, any class, any boat, someone can go out there and cheat. Unless you measure and inspect every boat on the water at every single race, someone could be breaking the rules, but do we do that? No, because it wouldn't make sense! There are a number of ways to say it, but, "is the juice worth the squeeze" is probably the one that most people will understand.
First and foremost, SCHRS will meet the needs of likely 95%+ of the sailors our there; guys like me who sail a Frankenboat are not in the majority. The semantics of "class legal", "stock" and "one design" could be argued for ages here, but... is the juice worth the squeeze? The point is, SCHRS states, "These rules are intended to allow a wide range of catamarans to race together. Boats from established classes with class rules must comply with their class rules and can use the ratings on the SCHRS list.
The other point in the SCHRS rules is this, "In case of doubt about any part of these regulations, the meaning, i.e. the spirit of the regulations governs." As such, lets just agree that, class legal is class legal. If you could take your H16, F18, A-cat, P19, N6.0, etc. etc. etc. to a nationals and race it without fear of being protested, you're good.
With that out of the way, 95% of the work is done!
Now, to the last 5% (that's a total SWAG guess, so don't hold me to it!). As Mark stated, the onus for how races are run is on the organizers. I might get myself shot by Jean-Claude for saying this, but... If the OA wants to use SCHRS, but allow sailors to measure their own boat, that is up to them. Again, Corinthian. As Mark said earlier, if someone shows up with a rating sheet that looks off.... like, a 20' boat listed at 4.9m, there's a problem. I would suggest that in cases where the OA wants to use SCHRS, but not require a full measurement certificate, the boat owner should provide not just a number, but a print out of their rating calculator spreadsheet with their entry. That said, boat owners should not expect that self developed rating to hold up for a larger race, or for SCHRS to approve it, because they won't.I COMPLETELY DISAGREE that the OA's should throw ratings/modifiers out there on the fly
... One of my biggest complaints (some people here will know what I'm talking about and this "major" race has yet to fix the problem...) is poorly developed NoR/SIs. Write the rules down clearly and unambiguously and publish them well in advance. If the OA says, "bring your own certificate", make sure the sailors know, fill out the #$@% spreadsheet, print a copy and bring it with you! Most of the people here aren't building their own hulls, they are taking an existing platform and changing the sails. There are >250 boats in the SCHRS table, surely almost everyone here can go to the table, take the published values and then fill in the blanks for sail measurements on the sail measurement form.
Although allowing/accepting self measured certificates induces a level of risk and reduces the integrity of the system, I think this is a more appropriate way to go than as Mark said, "PHRF'ing the number". If a racer doesn't like the measurement, they can go verify it themselves, but the rating formula and the integrity of the data that developed it remains the same. The other option is to use WAY outdated ratings from US PN and apply what are nothing more than WAG (not SWAG) modifiers. I'd prefer to put faith in people to honestly measure their boats than that.....