I don't think it's an easy problem to fix. Any pressure you put on the book elsewhere has the potential to damage it. The first iteration of the 3rd gen of holders led to a lot of problems (just look up "creep engine"). I think you could try and reverse that idea to make the slab concave in the center rather than convex, but that would probably lead to torn covers and damage from indentation at the center. If you eliminate the whole aspect of an inner "well" and just sandwich it between two pieces of plastic with a seam, then any overhang is in jeopardy of being damaged. Other than that, I don't know what the answer is.
And to be fair, the damage isn't caused by the well. It's caused by motion within the well. So the answer is just never ever move a slab, and then you're fine.