Thanks for the update. I almost understand the formula!
The big problem last year was that unless you were "resident" in Portugal and had a Fiscal number for paying taxes there was no way that you could actually pay the ****** tax. When this was pointed out to the booted brigade with the Swiss Admiral uniforms/badges, the reply was to the effect that it was the boatowners problem but that failure to pay would result ulimately in seizure of boat etc etc. I don't know if any boats were siezed after last year's effort. Any word on how this catch 22 will be fixed this year?
By the way, acquiring a fiscal number as a tax resident probably leaves you liable for Portugese income tax on your worldwide income - so not to be rushed into lightly!!!!