BandB,
If one did the St. Brendan's Isle for their personal address, they would still be liable for state use tax on the boat, regardless of where it was kept, correct? That's the way I read the statues. So, perhaps not a good choice.
Are the other "addresses" similar to St. Brendan's Isle, in more friendly states, that offer as much? I know one could get a private PO box most anywhere, but there are holes in doing that.
So, perhaps good advise for Selidster would be to find a state that has no personal income tax and a state for the boat that has no property tax, no boat use tax. Not sure where that would be.
Yes, two entirely separate issues are your personal residency and the location of your boat. As to the boat, he should figure out where he wants to use and keep it. Then see the tax situation.