I’m in the process of doing the same.I also went one step further and installed locking collars to the shafts so that I can adjust the tool heights in a more uniform manner for my auto tool zero system. mY overall tool length s about 3 3/4" long. I am also running these with my Hatachi 12c along with sawed down ER16-12 collets. I’m in the process of installing a ER20-16 in the Hitachi by cutting the shaft down to one inch and tapping the hole out to 10 mm, then taking one of my sawed off ER16 shafts and turning it down and threading it so that I can screw/red loctite it to the ER20 collet so It will fit my Hitachi’s 12mm collet.