Art, I fear you could be creating just more problems. There is a fraction of people already not up to their committment to the print exchanges; if on top of that they receive money coming from a tip-hat for not delivering up the print, then I fear there will be a form of "tax-payer resentment" going on from the part of the people who donated. This is not good.
I'm with Argus here: if you can actually afford to print your photos, you can afford to mail them. I've sent unmounted 8x10 RC prints in a PrintFile when that was all I could afford, and I don't think I've offended the recipients by doing so.