Here is one of the photo showing the white areas.
There is no weight table on the on the F.I's, as you said they should go in the spares box.
The area of round and rectangle white shapes are in the area of the plywood covering and would not be a fabric patch. To me they are access covers that are screwed in to the plywood. The edges are vary crisp to me that indicate a hard solid edge laying on top of the surface.
Taz and Greg would know more on this one but I'm guessing that they are access covers.
Lloyd...