Specific to the FL300 and the Buoy 44 boat. That was my boat and the experience of developing and racing it gave me a lot of valuable insight into both sides of this discussion.
First, the boat was officially measured for 2016 at the Islander just prior to the start. The forms were signed by Carla and submitted to SCHRS; I have the signed certificate and can assure you that it was not the same rating as a stock Tornado.
For 2017, I purchased a new spinnaker; besides the addition of rudder T-foils (does not affect rating on a boat with straight boards), the rest of the boat remained the same. The new sail was measured and a new ratings request officially submitted. Again, I have a signed copy of the certificate issued by SCHRS.
Overall, SCHRS did a very good job of rating this configuration relative to the N20c. There were times when each platform was in a more favorable range than the other, but you see that with any boat/race. In the end however, the race times supported the ratings for both platforms. We had several break downs, so we didn't perform as well in 2017, but I am MUCH happier that we raced under SCHRS instead of Portsmouth.
With regards to Portsmouth; the rating, once the modifiers were applied, resulted in the modified Tornado owing the N20c time! So, a boat designed in 1962 that is narrower, shorter and has pizza pans for dagger boards rates faster than a modern wave piercer with more volume, sail area and lifting boards??? Although the T did weigh less, that isn't enough to overcome the advantages that the N20c has in pure speed. This kind of handicap is the reason that we didn't run the boat in that configuration in the GT300; US PN over penalized the modifications and has not updated the F-18 to address development in that class. Note that there is still NOT a published rating for the N20c under US PN and that highlights one of its major problems; lack of support/updates over the past decade.
In that same line of thought, US PN relies on race data to develop ratings, once a new boat is released, it would take a year or more to come up with a somewhat "reliable" rating. SCHRS can rate it before it hits the water with a pretty high degree of certainty AND as race data is analyzed, make adjustments as necessary when anomalies are found. This is a good example of how SCHRS is handling the adoption of deck sweepers on the F-18, or foiling (among other changes) in the A-cats.
In the case of the changes to the F-18, the recent opinion of the SCHRS world council was to be careful to not make a decision that hurt the integrity of the system. In 2018, like every other year, data will be collected, analyzed and anomalies identified; the F-18 (along with a couple of others) will be under the microscope to determine if/how overall fleet performance was affected by the adoption of the new mainsail configuration. The data used for that analysis is from a much MUCH broader pool than is available in just the US. As such, the statistical significance is much higher.
SCHRS leadership is committed to ensuring the integrity of the system. A lot of work goes in to collecting race data, looking for problems and making sure that the system remains viable into the future.
If you have a few minutes and are curious, go read the annual world council reports available here: http://www.schrs.com/inc/SCHRS_Review_20180129.pdf
Previous reports are located on this page: http://www.schrs.com/news.php