Early 41 model history
One question I had was that early 41 model had a J of 16ft and longer boom (E 17?) and shorter mast (I 48). At least mine does (hull #3/1969). Later models appeared to move the mast back 1 ft with J 17, lengthen the mast (I 52) and shorten boom. Another variance is that early was single spreader where later was double. I was curious as to the motivation(s) for the change(s) and if there were other underwater changes like keel. The rudder was changed of course.