An Isotope meeting the One Design class specifications can be raced as a single handed Formula 16 boat. An Isotope with a spinnaker can be raced with crew in the Formula 16 one up class.

Just trying to understand this. I guess one-up they consider the Jib to be the spin? (F16 max jib area = 3.7m sq, Isotope jib= about 4.2m sq // can't race F16 one-up with jib) And, since the difference between one or two up on an F16 is in the use of the jib with no variance to the class or rating, what exactly does "An Isotope with a spinnaker can be raced with crew in the Formula 16 one up class." mean?