Thanks for the replies, Dave and Doug.

By way of update … I went to a third branch about 25 miles north of town (was already there) and cashed the check.

@ DM. I thought about striking out the stamp and photographing it with the strikethrough. I would then have a photo of the back of the check without the strikethrough and then with, which would evidence that I had made the demand.

A couple other ideas I have had:
-in light of the earlier post in this thread about the demand relating to transactions, the idea was to to make one final deposit at the bank with the transaction language and then call it good going forward based on that transactional demand.
- I may also just try writing in the demand as "lawful money demanded and redeemed, 12 USC 411" and avoiding the stamp and seeing what they say about that.

@Doug. Can you show proof that the IRS accepts the lawful money reduction for demands on the front of checks? I am glad to know this, however, I do not believe that writing under the signature is a 'trespass' as long as the writing is done above the line. Restrictive endorsements like "deposit only" are made all the time, and I feel that the non-endoresement should be underneath the signature so that the check cannot be negotiated further.