I have not heard any discussion of the ripple marks aft of the 4L door. This was the first picture I could track down, although I know I've seen some better ones.
link
To me, this can only be caused by a pressure event. I believe that these marks are just forward of the RPB. That means that the vertical split is right at the RPB and the outwardly ruptured skin just aft of the rippled skin would be aft of the RPB. To me, this indicates that the RPB gave way while there was still significant cabin pressure and was most likely the location of the initial depressurization.
Of course that still doesn't establish the root cause, but RPB failures are more than capable of taking out the HS and VS and have done so in past accidents. It could still be a planted explosive device or just the more mundane metal fatigue.
Comments?