My fork crown hole was already in use for a cable hanger, so I used some threaded rod instead of the bolt for more length in my canti brake mount.
I pasted this text from a previous post I made:
The headlight is mounted on a brake cantilever mount. It would have been easier to mount the light on the fork crown, but that is already used for the canti brake cable hanger, that is why I mounted the light in an alternative place. The brake mounting bolt was not long enough to be safely used, I used galvanized threaded rod and several nuts and washers instead. The light mount is an extra tall Edelux light mount, slightly straightened to get the light up higher above the fender and also move the rear of the light further above any tire spray on wet days. Used blue (removable) threadlocker and made sure that these nuts are all very tight, I do not want this to loosen since my front brake uses the same mount as the light.
More detail here, this is where I copied the text that I pasted above:
https://www.bikeforums.net/electroni...b-charger.html
As I noted above, I used the extra tall mount, the mount I used was an Edelux mount but that might be the same as the extra long B&M mount.