Hi Archie "if it fits..it ships" is their advertising so if you can put it in the envelope and seal it then the additional tape should not matter.. I have put the small flat rate box inside a flat rate envelope and not had a complaint yet from the post office. In fact that was one of their suggestions one time when I was shipping pins because the new small flat rate boxes are so flimsy. I might press the issue with the local postmaster if you don't mind pissing off the clerk.