I wouldn’t be greatly concerned bringing a closed PH boat down from NE in December. I did a delivery on a Sportfish with an open flybridge in December a few years ago (I froze my butt off) and we have constituently fished the Canyons 100-150 miles offshore for tuna in December and even January...
I was told by Nordhavn when discussing a potential future build that for the smaller boats 63 and smaller, expect 18-24 months unless crazy modifications are requested.