I finally got the holes in the right places for the mizzen mast step and partners, and for the rudder gudgeons. I drilled over-sized holes first, filled them with thickened epoxy, and then drilled the holes for the fastenings into the cured epoxy. This is so no water gets to the wood via the fastenings.
The bottom gudgeon was a little tricky, as the two bolts closest to the centreline had to be angled outward to miss the
transom knee on the inside with enough room to put a washer and a nut on. This was John's idea, to put them in on an angle—I wouldn't have thought to do that, but it worked fine. The upper gudgeon is an eye-bolt. I'd like
to find a threaded eye to put on the inside of it, as there's lots of
bolt coming through and it may as well be put to another use rather than just being chopped off.