Strategies for UAL waitlist

It's time for my annual trip to a conference the weekend before
Thanksgiving and I have a question specific to UAL Mileage Plus. I used
miles to get a standard coach award (40,000 pts) for a round trip
between ONT and ATL. What I really wanted was a Saver award for the
next class up, given that it's a long trip. I know that I should have
made a reservation sooner, but circumstances beyond my control made that
unreasonable. Now, when I tried to do this, I couldn't get a Saver
award at any of the airports within reach, which include ONT, LAX, SNA
and Burbank, CA. I am on the waitlist for a 6:15 AM flight form ONT to
ATL on my target day, Nov 21. Here's my question.

UAL said that I can only have one waitlist request for a
reservation. I don't know why but that's what they said. What is
important to me is to get to ATL before 5 PM on Nov 21, not leaving
before late on Nov 20. I really want that first class saver award. Of
the four airports I can get to for an early-morning flight on Nov 21
(there seem to be no really late night flights from southern Calif. to
ATL on the 20th on UAL), which would be the most likely to have a Saver
award spot open up between now and Nov 21? That is, if I can only be
waitlisted for one flight, should I keep that the one from ONT or should
I switch to he wailist for, say, Burbank or LAX, because the odds of
someone canceling their Saver award for that flight are better at
another airport? I'm not gripping. I know I'm responsible for the
situation. I'm just looking for a strategy to increase my (probably
dismal) chances of getting a seat in first class. Any suggestions on
changing my waitlist choice? Thanks.


Ken.