Ok, as promised a few weeks ago, a quick look at the method that we came up with to pack these specimens for shipping. I'm gonna state at the outset that I'm not really committed to this post, so if it suffers for quality, well, don't be surprised.
As with the Homotherium skull, we thought it prudent to immobilize the blocks of rock completely, lest they rocket through the side of the plywood when the package inevitability negatively accelerates from 80 mph to zero in 1.4 seconds. And like the Homotherium cast, we used polyurethane foam on the blocks that were 125+ lbs. Basically, I just packed a plastic bag between the wall of the crate and the specimen, then filled it with expanding foam. Here are some pictures.
One bag of foam was set on top of the block, then the lid was placed down to create a solid and tight fit. Finally, all of the empty space was filled with bubble wrap. That was a purely psychological move, as it would almost certainly do nothing if the rest of the packing failed in any way, other than maybe keep pieces from floating around if any chunks of rock spalled off.