Re: Not to nit-pick....
Here is a possible solution.
Add a line that says all flies to be fresh and tied with new materials.
Then if used flies are sent:
Send the used flies back to the swapper using the postage he has prepaid. Send the unused new flies that would have gone to the "used fly" swapper, back to the original tier. No one gets old used flies, and I would rather have one of my flies back than a used one.
No one gets any used flies and the used fly swapper gets the message.
"Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy