[franklinx]

I've never seen anyone test the flexibility, just the weight and whether it would go through the little slot dealie they have.

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Maybe watch closer, I have always seen them squeeze the package, give a lil bend as they ask you whats in the package. I did notice this less when I lived in Canada. But here, every time they ask you "whats in the package", and give it a tweak. Also more so here, they remind you of the list (contaminants etc) of things that cant go via post, and point at the board containing the list.
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Remember we are talking about post going to Canada from the U.S. not the other way around....=0p
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Pluss are you sending as a Photo/doc..?.. If not they are prolly just sending as a package. Not a letter doc.