Hoary old hide-bound traditionalist that I am, I hold with the idea that one should wear his father's tartan or, failing that, the tartan of one's mother. But I also understand that sometimes one may have to reach back quite a few generations before finding that Scottish link. Personally I think the "Three Generation Rule" is a good one, provided there is a mechanism to allow a Mr. Bianchi, who may trace his ancestry back further than three generations, to be recognized as a member of the clan.

My advice would be to write directly to the chief of the clan to which you have the closest blood connection and ask to be admitted to the clan under a bond of manrent. Historically chiefs have admitted "outsiders" to their clan in this manner, and once agreed, you are a member of his clan, full stop. Just remember though that most clan chiefs have to carry the burden of clan administration by themselves, and so it can take a while for them to respond to correspondence; likewise clan societies tend to be volunteer associations (often managed by the elderly) and this can also cause delay's in correspondence. If you haven't heard back in 90 days a polite "reminder" is not out of order.