74 (top tube) is 1mm longer than 73 (bottom tube)
BTW the Fleetboat section at Subcommittee has a number of things you might like to look at.
Things that need to be fixed to make a more accurate model including removing the doors on the side of the fairwater and placement of the venting holes on the bottom of the boat, exost openings, removing the broom off the mast.
More info can be found at AMP
Eric...