Thanks you for this info! With regards to the baggage allowance, my understanding is that the FMC allowance extends to the destination for flights originating in the US and Canada. Copa’s site notes this information, too:

https://www.copaair.com/en/web/us/in...baggage-policy

Both our United receipt and the reservation on Copa’s site show that all four of us get the two-bag allowance; on Copa’s site, however, it shows that we have to pay for the two bags, but only on the TPA > PTY segment. I’m pretty sure that’s not going to happen, though.

BTW, you mention that checking the bags through to VVI is against policy… is that United’s or Copa’s?