I remember this accident very clearly and in particular, reading about an 8mm movie camera that was recovered and used to estimate the vertical loads. After some searching, I found this Flight article which must be where I read about the camera:
https://www.flightglobal.com/FlightP...20-%201067.PDF
The film sequences showed pictures of Tokyo Airport, the Tanzawa mountains and Lake Yamanaka, followed by two empty frames, then by pictures of what appeared to be passenger seats and / or carpet before suddenly coming to an end. Tests showed that a peak load of 7.5g was required to make the film-feeding malfunction so as to skip frames in this way.
The article also mentions fuel moving foreward but doesn't refer to the horrific consequences for the crew.
Here's the link to the article referred to in an earlier post:
Japan - The Mount Fuji Disaster, by James Wilson (1966)
It's a very moving account by BOAC's Tokyo station manager.