I am flying LAX-HND tomorrow (9/21) and see that while I won't clear my PP UG (I am 1K) on UA39, UA32 (to NRT) appears to have 7 open Polaris seats (48 available, 41 booked, 1 on waitlist). I would need to pay a fare difference, but would be willing to pay it ($960 / seat) if I had reasonable assurances my upgrade would clear. The thing that is strange is that UA is showing 0 seats available for sale in Business (J0 JN0 C0 D0 Z0 ZN0 P0 PN0 PZ0) My assumption had been that this was an Economy oversold / Polaris available, but in that case, why would they not be still selling Polaris seats on this flight?

Any guesses on whether I'd clear if I paid to switch to this flight?

Thanks!