WheelsOff, for what it's worth, below is a quote from the PC office regarding inclusion of a hiring letter and some some of the other mandatory documents. Apparently some get kicked back just for minor errors (like dates not matching). This isn't all the documents required but info about the ones that typically are missing or cause a hiccup in the application.
"Intent to Hire letter from gaining unit showing tentative position (optional but highly encouraged)"
"AF 2631 Palace Chase Statement of Understanding (witness & mbr dates must MATCH)"
"Wet/digital signed justification memo (SAF PC will look at this)"