whats the best way to pack a third member for shipping

This sounds like the best way to me. I used to keep them in buckets they break right through over time . And that is just setting in the bucket and moving them once in a while. One handle you know they are going to be slamming it down.

I've built 2X4 frames with plywood, and then wrapped it with brown shipping paper. Put some rope handles on. Works like a champ, and fairly cheap.