I redeemed a HKG/YVR round trip upgrade from PEY to J and was only confirmed with YVR-HKG, HKG-YVR was on waiting list. The MPC operator suggested me to break the redemption into 2 single trips: HKG-YVR and YVR-HKG which cost 20000 miles per trip. He said if they could confirm HKG HKG-YVR at a later stage, I could call up and they would adjust the redemption cost from 40000 miles to 30000 miles (round trip redemption). Eventually I got through the wait list and called up MPC, they adjusted the two single redemptions to one round trip with 10000 refunded. ^