Reviving this old thread, all I can say is that the USPS is one of the most aggravating organizations I have ever dealt with.
To mail racquets I (used to) use a PO near work. Unfortunately, this post office was the home of the Mail N A Z I. If I printed my E-Bay mailing labels the night before, he would reject my package (at which time I would take it to another PO and it would be accepted). One day, I came in with two USPS boxes taped together for two tennis racquets, and he said, "You can't get the flat rate with that", and I replied that I had weighed it, measured it, and applied the appropriate Priority postage. He said okay. Two weeks later, I did the same thing, I was walking out as he was picking it up, and two days later it arrived at my house, rejected. I immediately covered up the rejected markings and successfully mailed it at another PO.
What is wrong with these people?