Hi, Brian. I'm not sure I'm following you.
On my second suggestion, I would modify your default file. I notice you are populating it with a database field... but remember, the DFP behavior is waiting for a form trigger so it actually occurs when the page reloads and that data field may have changed... so on your update page, I would create a hidden field that first get the output from the database and then make your default file become the output of the POST variable from the form to be sure that the default file is being set correctly.
What are you referring to by the default file? Are you referring to my included header file?