Excuse me for skipping the bulk of this thread and only addressing the OP, I'm basically just going through all these "unresolved" posts to make a point in another thread.
Anyway:
By disregarding gravity, you don't disregard simple laws about pressure and inertia. Put very simply, if 3 pieces of matter, a, b and c are stacked with a at the bottom and c at the top against an impenetrable blanket of matter which is pushing them upwards at an accelerating rate, c will be squashed only by the squashing power of b, b will be squashed by the squashing power of a and the added squash of c's squashage, and a will be the most squashed because it is squashed by the squashing power of the blanket as well as the compound squashage of b and c. I would have thought this was so fundamentally obvious as to not warrant explanation.