This is every sword plotted by length, with a high level confirmation… with the limit of a few o-dachi over 135cm. Just over 15,000.
Only about 10 years of work to get to that.
You can see various trends in here, the higher level papers show a clear ramp up in upper length (more ubu tachi present). The upper limit of wakizashi length shows clustering and we can see the longer wakizashi fall off the map when it gets to higher papers. Overall the strong visual signal for long swords shows that there is a clear preference for use in this range, and swords longer than about 78cm exist almost in a desert, they are so rare compared to the strongly defined standard length range.