Amendment

After the last post, I thought a little and found a solution of sorts to the problem of mounting that pesky rear fender.  Rather than rotate it back and up the seatpost

 I bent the plastic clasp forward and used a ziptie to attach it to the seatpost.

The clearance is still minimal, and not what I would want riding on muddy single tracks.

but there is clearance and no rubbing.

It can be done, but that's all it proves.  I doubt I will be happy riding it long with this arrangement.

A smaller tire makes more sense.