Louis Ohland wrote:
Drill into the lock washer, once through, whang away on the remainder of the lockwasher with a chisel.

Would that give you enough clearance?

It would, but that leaves me with the ball and nut unsupported in
the bumper. I'd have to come up with something to clamp the
ball in place so I could drill or slice into the nut and/or
mounting stud. I now have adequate clearance for my Mototool
after I drill the nut axially as per Jim Wilkins' suggestion.

That'll be my plan.

--Winston