Originally Posted by RobOnLI

Well, RN3 or RN2 makes no difference. Cancel the upgrade request by calling and then re-apply the PlusPoints online to get into PremPlus immediately.

Yes, United closed the buy-up loophole. If $300 is a buy-up and not a re-fare then you will not be able to use PlusPoints to get into Polaris. However, if you do a re-fare and flat out pay for PremPlus (O/A/R) then you can absolutely apply PlusPoints. Not only do you save yourself a bunch of PlusPoints (which doesn't sound like your motivation) but you also move higher up on the list per my previous post. However, you will almost definitely screw up your return. Technically if you re-fare it has to rebook all segments into the class of service you are paying for. All upgrades go away and PPs are refunded to your account. Does the return flight still have PZ open? If so then this is an easy change. If not then you are taking a huge risk because there's no guarantee that you giving up your seat will force PZ to open again. In all likelihood it will not. Now, having said all that, a very good UA phone agent can take care of this change while preserving your upgrade but technically that's not how it works and you may not find an agent willing to do it.

-RM