I am booked LAX-SYD on an L fare. Just called to ask if I could upfare so I could apply my GPUs to the reservation. Agent said no problem, and that that she would be happy to waive the $300 change fee this time. Fare difference was about $460, but nothing like the $9000, if I was to book into C directly. Worked out well, but the system was definitely going to charge the standard change fee. Outbound waitlisted, return cleared at time of application.