Many thanks for your contribution.
My take on is that as with much modelling of things historical, a bit of guess work comes into play.
I note that you mention the load being off centre and that you think that it might be there for scrapping. My interpretation is different in that I think that the off centre look is due to the angle the photo was taken from than it actually being off centre as such but I may be wrong. The reason that I think that is when zooming into a larger scan I think that I can make out fixing plates across the under frame beams fastening it to the wagon floor and I wouldn't have expected them to have done that off centre.
If it is off centre that doesn't necessarily mean that it's waiting to be broken up it might just mean that it's static in the siding and any vacuuming is done from that point (all pure speculation on my part).
Since it's all conjecture I plan to make some mounting plates and fasten it to the wagon floor in a similar manner as I view it.
PS I am the Rob Pulham (not Pullman
although you are by no means on your own when seeing it as Pullman, I guess it's what people expect to see) that you link to on Flickr