I'm going to throw this out there and see what people think. I theorize that if the eggs are held immobile in the boxes then the contents of the egg are going to receive the brunt of any jostling.
Let me illustrate it this way. Old cars had much harder bodies than cars today. You could hit a tree and barely make a dent in the car, but injuries to the people inside were much more severe. Now the outer shell of a car crumples like an accordion but people walk away because the shell of the car absorbs the force of the impact. All the force has to go somewhere, you know what I mean? It's basic physics.
I think the eggs make it best if they're packed in something that gives around them, like peanuts. Foam itself is great, I just think that if it is in a solid block inside the box then the only "give" inside that box is the contents of the egg.
And I'm the person fifelakelooper referenced that had 2 broken and 1 cracked in foam. Some of the eggs that weren't outwardly damaged had ruptured air cells. *sigh* I'm hoping that 30% of the number shipped will hatch, because that's what's developing now. I don't blame the foam, mind you. I blame the Post Office. The eggs were very well packaged and the seller sent lots of extras so all I've got to complain about is the PO(s).