Originally Posted by
SnowAndSun
I'm not planning on asking for an UG - I'm planning on making someone's day by asking them if they'd like to have my F seat, in exchange for their seat next to my S/O.

They might say no. If they are traveling with they own SO, for example, they may not want to separate. How full is the flight? I trust that it's not very full, since they EUA'ed a Silver. If it's not very full it should be okay, you and your SO can always move to somewhere else in coach, even if your F seat goes empty.