Hi GreyGnome;
I guess I am unsure of what you are trying to accomplish then. Generally speaking, the backup and running of pt-table-checksum are used for separate purposes. The backup portion is fairly straight forward; you just want a valid and consistent point-in-time backup, which Xtrabackup will give you. Then when you run pt-table-checksum, you are generally making sure that the slave(s) are in-sync with the master.
So the question is, what is your intended purpose with running pt-table-checksum in this case? Is your backup on a slave, and you are wanting to check each time to make sure the slave is in-sync with the master? Or some other purpose?
-Scott