Let's make this perfectly clear (Wouter):

The 16 w/Spinnaker is NOT class legal on a general basis.

The wording from the International Hobie Class Association Class Rules:

Quote
Appendix B
IHCA Supplement to the International Hobie Cat 16 Class Rules.
THE USE OF THE SPINNAKER IS ONLY AUTHORIZED FOR SPECIAL YOUTH EVENTS.


I did not add the emphasis. It's in the rules.

Go here if you want to check it yourself.