Ed, your bike looks almost identical to mine!
A red GS with BMW tubeless 21" wheel....
Curious to see what you end up doing with the fender.
I got a chance to get one of those Wunderlich fork clamps for a very good price so went that route. But I didn't get the Wunderlich fender.
So far I cut a stock fender in half and attached the front half to the Wunderlich fork clamp.
I still need to make something for the rear half of the fender.
"It is not when or how you die but how and if you truly were ever alive!" Dr. Jerri Nielsen FitzGerald