Admin note: A gentle reminder that online our words are all we have to represent us, unleavened by subtle visual cues like a grin or twinkle in the eye that are left unseen. Best to be polite and gentle with the words chosen. We do indeed enjoy a rare gentility here that is missing on most forums.=====
That said, I have a 1989 touring bike that arrived with a 6mm threaded hole in the front of the fork, but none behind, making for difficulties in securing the front nudguard mounting tab. I carefully marked the location, setup a fixture, drilled, and then threaded a similar 6mm hole in the rear of the crown and it has functioned well ever since.
However, this was a forged crown and not all are. Similarly, not everyone is equipped to do such work and there are potential warranty issues as well.
Snoog', I think yours is a clever solution and I certainly understand the need for quick 'guard removal/reinstallation for Rinko use (partial disassembly for bagging while on a train or other public conveyance). This can present some devilishly difficult problems. For example, in Japan (where the term originates and the practice is more common), there exist rear mudguards with specially sleeved joints to reduce their length in mere seconds. Similarly, front 'guards are made to detach quickly. If the fork needs turning to make the smallest package, headlights can foul the downtube. For some generally helpful Rinko packing tips, see:
http://www.bikequarterly.com/images/BQ_rinko.pdfHmm. Cronometro makes a product called "The Nob" that fastens to a fork blade to simulate a handlebar for mounting lights. See:
http://www.peterwhitecycles.com/light-mounts.php#nob Minoura makes a similar product. However, the location further down the fork leg does expose the light to more wheel-spray than your method, Snoog'. I do recall some front reflectors made in the late 1970s used a bracket that attached to the brake bolt at the rear of the fork crown, then extended forward under the crown before popping upright to present the reflector. Perhaps something like that could be used, though perhaps less elegantly in the end.
All the best,
Dan.