Call the 1K line and see if there are dates/routes where the upgrades can clear on booking. (we did this in March of last year for a trip to China, w/ both of us having confirmed upgrades, via SWU, on booking. We used an unusual return, suggested by another FT'er, to get flights w/ upgrades HKG-sin-nrt...MSY. Upgrades cleared on booking. It was a lengthy return, but the cheapest mileage run ever, as the strange routing was several hundred $$$ less than the more direct routing and about 3K more miles)

It's probably harder to do so now, w/ fewer C seats available, but as you know the dates and may have some flexibility, i.e., arrive a day early or whatever, it could be worth a call.

A downside is that if trying for EQM's from use of the Chase credit card, this probably won't qualify, at least not for EQM's. (I had our reservation put on hold, went to .bomb to book, but never got EQM's for that booking). To Chase EQM's, ask for dates available, then book it yourself on .bomb, then apply SWU's, if they don't work, cancel w/in 24 hours and start over or make the reservation by phone.