Heres a nice mounting of a Cyo (Dynamo) front lamp on modern Brompton M bars
(using supernova bracket: would this schmitt be any good/better I wonder
https://www.sjscycles.co.uk/lighting-spares/black-schmidt-headlight-bracket-for-delux-milled-318-mm-clamp/ ) ?:
http://sitrickett.blogspot.co.uk/2013/11/brompton-dynamo-light.htmlwhich, compared to standard official low fork mounting, should allow further illumination of road whilst still being properly dipped 1.5plus_a_bit to 2-ish or more degrees below horizontal to avoid blinding people on rough roads.
I have come to the conclusion that the official low mounting point means you have to accept a shorter beam reach, if you want to dip the beam correctly and for it to remain dipped on rough surfaces....
I feel a high mounting point is also better in urban areas (avoids need for extra be-seen handle bar battery lamp).
Disadvantage: need to remember to remove lamp before upturning bike for emergency roadside maintenance
.
Disclaimer: my brompton is currently battery powered at the front.