I never wanted to say that the spi is CLASS LEGAL for the BASIC H16 class. Just that the H16 has a class legal spinnaker in its ISAF YOUTH CLASS setup. Which is a H16 class as well, at least many claim it to be such a thing. This youth class is certainly not a formula class or whatever.
The appendix that you quote supports this. Also the youths are not sailing ANY event without the spi. The fact that it is only authorized for special Youth events is just silly. These youths need to practise, right ? Overhere the teams seem to sail any open class event with the spi package.
In summary, the H16 design now has an official regulated spinnaker package that is supplied by Hobie cat corp. Although according to the hobie class rules only youths may use it. I would personally call such a thing "class legal". Others may see that differently; of course.
But hey ! why do the kids always get the fun stuff ?

I wonder what these kids will do when they turn senior and are faced with a choice between a spi-less (senior) H16 class or one of the other spi classes ?
Wouter