Being an ex postal employee for 20 years, I know it can be done. Remember the rule says it can not VARY more than 1/4 in in thickness. It does not say it can't be over 1/4 in. That is the easy part, getting the clerk to agree with you is the hard part. Some will, some won't. I usually go call their clerk supervisor to the window and show them the printed page from their regs. Good luck. Go to the main PO and ask for the person who trains the clerks. They usually get it right.