SMR no is 4 shaku 2 sun 1 bu.
Jonathan wrote a fine article. Let me add my website on wood for Japanese wraponry www.zaimoku.org
Bruce Bookman and I are engaged in the development of a new approach to aikijo- currently working on a set of 5 kumijo. Using 5 shaku (feet) hickory JO.
A very good article by you.
I am very interested to see what you two develop!