From the www.hobieclass.com website:

ISAF have maintained the Hobie 16 as the ISAF Youth boat

The ISAF Council have again approved the Hobie 16 with spinnaker as the ISAF Youth Multihull to be used at the ISAF Youth World Championships. ISAF did add another boat to the multihull discipline (the organisers are allowed the choice of two manufacturers in the disciplines) but as yet it can not meet the ISAF Regulations so it can not be considered for ISAF Youth Worlds.

SO THE HOBIE 16 WITH SPINNAKER REMAINS THE ONLY BOAT THAT CAN BE USED AT THE ISAF YOUTH WORLDS.

Hobie Cat Forums
Matt Miller
Hobie Cat Company