When an extractor receives cash, no matter how small an amount, he has to take it to a special desk and fill out of few nasty forms. Write a little letter of appreciation. Any letter received has to read and stamped regardless of what it is or what its on. Write your letter on something misshapen and unconventional. Like on the back of a Kroger sack.
Big envelopes have to be torn and sorted differently than regular business size ones.
An added bonus to the big envelope is that they take priority over other mail, so the workers can hurry up and deal with your mess. If you send 2 checks they'll have to staple your unsightly envelope to your half destroyed form. Always put extra paper clips on your forms. Any foreign fasteners or the like have to be removed and put away. Sign your name in ink on every page.