Idle speculation:
Litebulbs comment about the O2 cylinder visible in post 358 pix #2 looks right to the eyeball. From the same pix, the white harness dimly seen just forward of the green object looks as though it might be a collection of four to six white tubes for carrying O2 toward the cabin.
If another O2 cylinder were located just forward of the green shape in the pic, then its lower end might line up rather neatly with the bottom of the visible hole, and its upper end with the tongue of pressure hull skin bent outward at top of the damage area. A pressure cylinder failure originating near the base of the inside surface would provide rocket power to propel much of the disintegrating cylinder outward and upward in a manner consistent with the observed hole.
How would a high-test cylinder suddenly decide to disassemble in this manner? Perhaps the very same cargo pallet visible in the post-incident pictures included a rock or ice-climbing pick - with a very sharp, hard steel point (or something similar..hard, pointy) and some still unexplained shift of the cargo bulk brought this chisel point in contact with the pressurized O2 cylinder, allowing vibration to hammer away at the surface and eventually causing a stress failure at the lower inside-facing part of the gas container - with results as now may be seen.