To anyone else out there who had similar questions regarding sailing non-stock Hobie's in Hobie events I e-mailed the NAHCA and received the following response from Rich McVeigh (Rich, I aplogize in advance if this upsets you, I just posted it as information to other interested parties, if it upsets you let me know and I will remove it).
Basically what it means is that if the boat has any modifications not permitted in the class rules for that particular boat they will not be allowed to sail in Hobie Class Sanctioned Events.
"In order to sail in any Hobie Class sanctioned event you need to ensure
your boat in compliance with the IHCA class rules as outlined on the
IHCA web site at www.hobieclass.com
. Specifically this would mean that
no a spinaker is not legal on a Hobie 16. You are of course able to use
your spinaker in non-class sanctioned events and open events scored by
portsmouth. You may ask how can I tell the difference? The type of
event you are entering should be clearly spelled out in the notice of
Hobie Class Chair"