I finally had time to respond to the UA 1k response to my initial letter:

"Thank you for your response.

Unfortunately, it does not address one of my primary concerns--the
upgradeability of Silver Wings tickets. While in the last couple of days
general agreement has returned to the belief that they are fully upgradeable,
I would like to see it in writing.

Could you also, please rephrase your response to clarify general upgreability.
I am afraid that I was quite honestly more confused after reading it than I
was before I read it. I am simply attempting to gain understanding of what is
and is not upgreable to eliminate the necessity of making and cancelling three
or four reservations for every trip, until I happen to hit on one that works.
This practice is a waste of valuable time for both me and the very busy UA 1k
agents.

Thank you for your attention to this matter."

OBTW, the 1k e-mail now generates an immediate canned response.