Yes, another one of those clearly worded Administrative Rules!
Sometimes it is necessary to go back and determine the intent of the legislation or rule rather that interpret the gobble-de-gook that finally gets penned in to law.
Anyway, the intent was to help differentiate a three or more person in-line jet craft which is for all intents and purposes a vessel in New Hampshire, vice the one & two seaters that are for all intents and purposes jet skis and thus subject to different inland waterway restricitons on (some occasions)!
That said, the sticker is optional and requires the registered owner to separately apply for same. It allows for authorities to visually determine the vessel's capacity from a distance rather than having to stop the vessel and ascertain its carrying capacity via the registration.
And has been previously noted by several posters it is a very little known regulation that is rarely employed.
Obviously it would have been much easier to simply issue the appropriate sticker at the time and place of registration if indeed the state was looking for mandatory and widespread implementation.
By the way, the key legalese that is missing from the quoted rule that would have made the decal clearly mandatory?
Two simple words:
SHALL DISPLAY
Hope this helped explain it a little better.....