I don't know exactly where I heard this, but I think it was at a Friends meeting in Chama. Evidently during the oil boom, the wood cars WERE showing their age. This is especially true of the idler flats, which being cut-down house cars lacked the structural integerity they were built with: the rail didn't quite compensate. You all know that these were cut in between cars to allow pipe to overhang in the 30' gons. Well, the flats had a habit of breaking in two! The train rumbling along and POW! everything shuts down as the air is lost and the brakes go into emergency. Imagine the crew going back a few cars to find a pile of splinters where there used to be an idler flat. I guess the railroad would send out a cat and push the whole mess off to the side of the track, couple up and resume the trip. The resulting pile of sticks would assume the name of the engineer in question, as in "Jones' flat." A bit of color for a modeler to add to their pike....
I am not surprised that the Grande did not send trains over the road with blocks of steel cars grouped at the head end. For the little I know of railroading, that seems like an awful lot of work and consequent head scratching for the crew assembling a train. I am sure that the photos John and others have consulted indicated that the loaded trains were pretty well mixed batches of wood and steel cars all the way through.
Keith