Also, this is what The Gun Zone has to say about the PO thing...

The Concealed Carry in the Post Office
Analysis by Robert P. Firriolo, Esq. usually at
this URL has been removed pending a review
in light of recently revised U.S.P.S. regulations,
specifically a new introductory clause to 232.1
.
So whatever it did say, I'd forget about it for now.