Originally Posted by canopus27

Agree with this, but the other line I would also ask the gate agent is "please tell me when the J and PY cabins have boarded full"

Once the cabins have actually boarded full, it's very very unlikely that anything will change (technically someone could offlload, but that's not at all common) - so if the GA can tell you once they are full, you can then board Y and not have to be the very last person looking for bin space