It's really hard to tell. COPA does not have the R/RN buckets like UA. I am sure that if they are showing D you can use an RPU and probably even with only C class.

I responded to your other post in the UA forum. That has a link to instructions on how to use an RPU on COPA. You have to book on COPA and then call the 1K line. It's a pain in the neck, but it's worked the two times that I did it.