I acknowledge it is not answering your question, but as I understand legally it has to be registered. I know that the US turns a blind eye to it here in the
PNW near the border where there are so many
boats going back and forth, however with other countries I have always had to provide the
registration number. I expect in some of those counties they would not have a clue if I provided the wrong number..
I'll also be interested to hear the answers to your original question.