Should also mention the ratings were developed in conjunction with production boat manufacturers. They are only rated for suggested service at the time of initial launch.
Blue water sailors commonly do not trust the system because of this. Depending upon the quality of build some boats are A at time of build and with average maintenance remain A even after years of service. Others may have been A at time of initial splash but even without modifications and with good maintenance are no longer A after a limited period of
modest use.
Details like how bulkheads glassed in or retained by tabs. If not stick built what adhesives were used and if done in controlled settings or not. How deck hull joint was done. Even little things that might allow water ingress and delamination such as deck fittings install.
Personally have little faith in this system having seen too many A boats I believe are unsafe for passage. After a short period of use they are old and tired. In afte cases the reverse is true. Some motorsailors are strongly built but rated B as the pilot house doors slide and aren’t hinged. Personally believe they are much better built than some French production boats and better sea boats.
