Grant,
The lengthly Canadian HIN information that is in government-speak is geared towards commercial builders who are producing boats for sale. Most of the regulations have nothing to do with the home built, except for one page, in which you need to fill in and send in for your decal. I have had many customers who have phoned and been given info on how to apply, not realizing that they were applying for a commercial number.

The latest said he phoned the federal dept. and the person had no idea what he was talking about for a home built number.

As for crossing the border, most times there is no problem, but should they ask and you can not prove you either built it or bought it in your home country (are not trying to smuggle a purchase across the border), you might wish you had some identification. I have most trouble returning to my own country (Canada) with boats, but they are concerned that I might have been trying to do business in the US without proper paperwork. Which is somewhat of a catch since someone who is business for themselves is always in business, no matter where they are or what is the purpose of their trip.

If you are in Canada, there are regional offices of the coast guard that may be of more assistance in determining which form is required and how to fill it in.