I have never thought of this question before and can't say that I've seen it answered before:

I have a flight ORD-SFO coming up that I was not CPU'd for at T-96, but I think I have a reasonable chance of getting the CPU at the gate (it's a 757, so quite a few seats in first).

I'd prefer to save my RPUs of course if I can get the CPU.

What if I were to check in, view my spot on the waitlist around T-5, and apply the RPU then if I am not at #1/2? Obviously I'd have to call it in, but wouldn't it be possible to un-checkin myself, ask for the RPU to be applied, and then check back in?

Thanks,
Patrick