Hi Arjan,
Having been a modeler for the better part of 3 decades, I understand well the leeway this hobby affords to a man seeking to play with dolls.
My solution - a raid to the local toy store for a suitably dressed Ken @ 9Eur. After all, the Princess is modelled after an Italian runabout, and you only see those in "expensive" northern lakes. Way I see it, the white tux fits the bill and goes well with the white leather. Maybe also a Barbie with bikini on the sundeck later on just for the laugh of it.
The Mattel figure is about 28cm tall, which would make it about 1/7 scale (OK, this pushes it to a 2m tal full size man, but you are Dutch..). So, a 1/8 scale boat with 1/10 fittings and a 1/7 scale figure... yeah, life ain't perfect but we gotta work with what we have!
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Hope it will not look too rediculous in the end. If it does, then I hand the doll over to my 6yr old daughter and live with a "Ghost" boat (no driver) - no harm done.