: At 1:59, you are marking the line on the "to be trimmed"
: side of the batten, yet at 2:05 you are marking on the "not
: to be trimmed" side of the batten, what happened?

Magic!

No, I had to move the spline for marking the center line to get all the way to the stem. In doing so, I decided it was easier to put the spline on the other side of the keel. Either side works, it is the line that you draw that matters.