Good job finding the Florida use tax FAQ page, Boatpoker!
here's a page with Letter Ruling on Reciprocal Hailing Ports
that are not charged fees
for the US Cruising Permit
If laws, codes, rulings, and regulations
were literal and straightforward there'd be no market for lawyers and their services. As far as boat Use Tax goes, there's still the matter of when someone becomes a Resident of a state for purpose of taxation (not citizenship). I think even a foreign flagged vessel needs to keep moving around every 90 days IF in an area with aggressive tax collectors. Tax collectors interpret the laws too, they sue and get sued.
This is an interesting thread. Now I understand why I see mega-yachts hailing from small island British Dependencies. I will keep digging around code and hope others (Boatpoker!) will too.