I wanted to say a quick thank you for all who've contributed to this thread. Applied a RUC and was unable to check-in. Called-in and was told "oh it's fine you'll be able to check-in at the airport." Called in again after reading the wiki and got an agent that immediately said 'good news! your upgrade cleared. Let me just take 5 minutes to reissue your ticket and you'll be all good.'

I do realize that it may have been fine at the airport, but now I feel even better that the RUC cleared!

Thanks, FT!