I have a question about combining waitlisting and confirmed upgrades.

Calling quite soon about a three-flight itin I have coming up, LHR-YUL-YYZ-DEN. I class is available on all legs except the first one, LHR-YUL.

Can I confirm the other two legs, whilst waitlisting for LHR-YUL? If it comes down to it I don't mind burning a cert for YUL-YYZ-DEN alone.