Attempting to SDC a non-stop upgraded with a RUC to a connection, I had problems with several agents who didn't understand that what I wanted was permitted by the rules (any available (F) seat).

Does anybody have a reference or the magic language I can use to explain to them what they should do/how they should do it?

One problem was that the ticket hadn't been reissued (cleared right after purchase, not reissued 24 hours prior to flight).