Hobie Europe sells a spinnaker kit for the 16 that is used for one-design youth events only - most notably the ISAF World Youth Games.
It's very pricey ($1,500+)
The Hobie Class Association in North America is vehemently opposed to introducing it as a one-deisgn racing class in the US for a number of reasons, not the least of which is that it would split the existing Hobie 16 class in two, further diluting fleet sizes at regattas.
Think of past history:
Hobie 14 > 14 Turbo
Hobie 18 > 18 Magnum > 18 SX > 18 Formula
Hobie 17 > 17 Sport
With the exception of the 17 (which never allowed a 17 Sport racing class), all of these derivative classes have failed.
The Hobie 16 is the most active, most competitive one-design
catamaran class in the world. You want a spinnaker to race one-design? Get a Tiger or a Dragoon.