Keep in mind that 7th and 8th Rgt. were told all mail should be sent NLT 7/10 if you want to make sure it is delivered before your cadet leaves Ft. Knox...They do not forward, and rarely return leftover mail...(Not sure how they get away with that, but it was true in BCT)...
Do you know if that included priority mail too? My DS (also 7th reg) just asked me to send him something rather important (can't believe he actually wrote a letter) and I was going to send it priority mail.