After nearly two and a half years, this happened:
Yup, it broke just where I expected!
The front fender on Mary’s bike suffers a bit more stress than you might expect, as she must wheel it through high grass to her Vassar Farms garden plot and the low-hanging spray flap can snag on the taller greenery.
Re-slicing the original model, printing the result, and installing it took about an hour:
Affixing the strut with duct tape and a cable tie looks déclassé, but continues to work better than anything else I’ve tried: simple, flexible, easily readjusted, totally nonfussy.
At least I now use black outdoor-rated double-stick foam tape, so life is increasingly good …