I had an OEM CPU sent pressed into a bit of foam padding, then put in a small card box (maybe a 2" by 2" by 0.5" or a bit bigger), and there were no issues.
On a vaguely related note: How much might it cost to send a CPU packaged in the manner best desribed in this thread from the US to the UK? ie: just proc with no HS, in a small box or plastic case or whatever.