I got the same problem, but a way bigger, with floor and futtock riders of the Hoy (Antscherl wasn't even sure the were foreseen in theactual ship). I spent maybe an entire day on any single piece (6 overall) and, in one or two cases, I even had to repeat the job two times. For the mast steps alone I suggest a "3-D template" of some soft wood stripes (finally glued together), each carved accordingly to the hull and centre-line shape in any given point. Once you get the 3D template, you can copy that more or less precisely, taking measures here and there. The other way is... long and patience file work, tenth after tenth of millimetre, until the mounting fits perfectly. Anyway, enjoy the project! Kind Regards