I suggest that the individual members of a set of metric setup bars be chosen so that a wide range of exact dimensions can be set. For example, if the set included 1, 2, 3, 4, 5, 10, and 20 mm, you could create just about any combination from 1 through 39 mm. If the set is intended only to be used with Festool routers, fewer setup bars would suffice if the user is willing to use the built-in micro-depth adjustment feature (each turn of the dial being one millimeter).
I also suggest we collect multiple data inputs for each brand of PC style bushings, because each manufacturer is also going to have manufacturing tolerances for its own production. That tolerance data is seldom published by a manufacturer and commonly held as a trade secret. That could explain why my the PC style bushing of my Whiteside inlay kit would not fit the adapter supplied with my Festool 1400 router until I filed away some of the external threads.
Dave R.