I put in my own packaging size once and the printed the postage slip, then went to my AP and they scanned the barcode and nothing came up on the system. This was one that I had to pay over the counter at AP and I explained that to them but they kept saying the barcode doesnt scan up and they had no idea what to do.

So I stopped using my own pakage dimensions and was less hassle just charging an extra $3.20 for Registered Post