Thanks Den1 Thanks Oddjob!
The later mounts got a thin rubber washer glued onto the fork ears. So your idea is a good idea as well.
I noticed the metal nut plates, 'inside the headlight shell, have a glued rubber pad. But there's no paint to protect inside the headlight shell, so I assume the pad provides a little isolation from vibration.
I also considered using thin rubber washers on both sides of the fork ears but thought the nylon might be less likely to 'stick' to the paint than rubber. Dunno?
Were the rubber washers you mentioned on the fork ears of later models on the inside (headlight) side of the fork ears? With just a flat washer followed by a lock washer on the winker stud on the outside of the fork ear?
ZT