Just have a quick question for those of you who might have some experience with this:

Can you upgrade to Envoy at booking using miles (subject to availability), then at 7 days out from the flight swap from using miles to using a CP upgrade cert if they still have the appropriate class open? Theoretically, just by giving back your miles-upgraded seat availability should open for you to use your upgrade cert. This sounds too good to be true, but one can always hope...

I know you can cancel award tickets and get the miles back, just not sure on upgrades using miles.

I apologize in advance if this has been asked and answered.

Thanks!

Sean