I mailed a 25 lb. Priority Express International package last week, using a double-boxed Priority Mail LFRB that was taped to the gills on the outside with clear shipping tape.
Postal worker at my local branch (he knows me well
) just looked at it and said, "That might cause some confusion."
He then proceeded to tape the ever-living shit out of it with "Priority Express International" logo shipping tape, to the point you couldn't even tell what kind of box it was originally.
There were only a couple of open plain white spots left where there wasn't any PEI tape at all.
Too much tape, my ass. Tell 'em to pound sand and show you the guideline in print that backs up their claim. Same for double-boxing, so long as it meets size/weight/content specifications. Cardboard is not on the prohibited list.