I was able to do that in the last month or so. I had a Zephyr trip initially booked at the 2nd highest bucket. I kept checking and it dropped to the 2nd lowest bucket and then a couple months later to the lowest bucket (a week or so before departure). Both times I used the "modify trip" option...
Applied and was was approved for the Preferred card using an email address different from my AGR email address. Today I received emails welcoming me to AGR with a new membership number using the email from the card application. Not ideal.