The boat was assembled from pre-cut parts back in the days, and frames was supposed to be assembled tight. I guess 1/4" - 3/8" gap was close enough. I also think the half-round holes was drilled after frame was assembled and bolted in. They have different placement and size from frame to frame. This one is is also drilled at an angle.
I'm also waiting for the profile drawing of the hull from the Mariners Museum. I hope this will tell me if and how much concave shape the frames have, especially the aft 3 or 4 on the planning surface. Can't seem to get it to look right with battens and straightedges.