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Jon, why not do it in the form of a small drawing show? Recently I just sent 2 pieces to Don Farrell in Seattle, in an envelope (as a letter, A4 size), and ordered frames from Dick Blick art supplies to have them shipped to him. He framed my work and it is currently showing in Seattle. Should I want them back, he can return them the same way and keep the frames for his trouble, but likely I will keep them at his place there for future shows in the US. He had shown 3 other works of mine before already. Miguel Tio in New York has several of my pieces as well which he puts into shows whenever he shows his stuff (usually with AOI in New York and Montreal).
When I was assistant curator at the UofL Art Gallery in Canada, we imported a show of Surrealist drawings from Spain, which was a small parcel that arrived under the radar of customs, and we, as a gallery, had a whole bunch of quick-change aluminum frames just for such occasions (most public galleries in Canada do - sort of like a standard). I framed that show within an afternoon.
And you should know that for the "Exquisite Corpse" cooperative works we send stuff back and forth all over the world in envelopes all the time. The postage for a medium size (letter size) envelope is minimal - and: NO CUSTOMS!
As far as I remember, when I shipped my drawing to you (way back when) from Canada, in a tube, it didn't cost that much either, and if the value given is not astronomical, customs does not even bother with it (like: under $ 300.- or so). But envelope is the best, because you don't have to "cheat".