i use flat rate boxes all the time and ship fabric/quilts all over the country and canada...i understand the envelopes being used for documents. i don't understand your issue?... selling-sending just small amounts? you can use tyvek envelopes, that's what i use for all my swaps and smaller than a box full of fabrics. if you pick up a scale (available in office supply places-even walmart carries them) you can weigh your envelope-packaging and print your postage from your computer so it's pretty easy to figure out how much it's going to be. i find the usps web site one of the more user-friendly ones for shipping. :thumbup: