[Alex van de Wetering]

I always see the FAT-5 7B3 body as closely related to the 6x6 FAT prototype.....and indeed the 6x6 prototype also seems to have been fitted with these low back seats (back compartment only, fronts are "normal" CMP seats).

Bit difficult to see, but It seems in the picture attached only the outside 2 seats have been fitted with cushions on the back rest, while the two in the centre seem to show the steel plates as also shown in Mariano's picture.

picture from the RCEME website