Great, thanks for sharing your experiences! My LBS recommended going with a hard-shell bike shipping container, but I do know that friends of mine that have done Ironman all over have used a cardboard box. But they typically just take the bikes on as checked oversized, so I think it gets handled a bit better than post.
My mother mentioned that the next time she comes to visit, she might be able to bring it along. Perhaps that would be the most cost-effective and safest route after all.
But please, if you do have other experiences to share, keep them coming.

Sara
There's only one thing better than spending a day on my bike: Spending a day on my bike in good company.