a couple hours ago I booked SEA-RDU-DCA thru Concur for an Apr trip ... hadn't cleared C+ upgrades yet, but when I opened the app and looked at the F cabin I could select seats for $203.38 and $52.68 respectively
called in, discussed w agent, and confirmed those prices would NOT cause the ticket to be reissued into Z (I"d get MQD, but not the 50% class-of-service MQM which is more important)
$328 for upfare was entirely acceptable however