UG,
I am sorry about the postage due.That really ticks me off.
I stood right at the counter and watched the clerk put the necessary postage on both envelopes.In fact both packages were stamped for PRIORITY MAIL for a total of $9.00.I think the next swap I will put the postage on myself and add a layer of clear tape over the postage so it can't come off or should I say be tampered with. I have a cousin that works at the post office and I will ask him how often does this happen.