Being the OP of this thread I am obviously very happy to see how it has helped shape change shipping practices to safer methods using non permeable packaging. Customs are not sitting idly by though and I have it on good authority AU customs have changed their tactics, they may be scanning more letter mail than before or as someone recently suggested to me they could be using other methods to detect MBB, e.g. metal detection. I have no solid proof of either of these theories but having recently lost an MBB'd order from a vendor whom I trust, I can therefore only conclude that my letter was subjected to something more than a canine sweep, or I just got unlucky, who knows... So I open this up for further discussion, it is good to keep evolving so now I am going to see if there are MBB's that do not have a metalized layer.