Double Heading up Marshall Pass?

John,
You said double heading up Marshall Pass was prohibited? Was that a specific timeframe? I have seen footage and seen pictures of doubleheaded freights with a third pushing on several occasions. (WB's 1940's Memories)
The big Four Engine Stock train of 1948 had 490 & 496 on the point, 495 cut into the train and the 498 pushing (behind the caboose if you believe the reports) (From the Stock Car Book from a few years ago)
The 1950's version of the Four Engine stock train (this time with K-36's) included one at the point, two coupled together in the middle and one rear pusher.
Also regarding the Doubleheading from Durango to Chama, I have heard that the up and downgrades along the line from Dur to Chm would cause slack action in the train and possible derailments if a rear engine were used.
I have footage of Three-Engine trains up Cumbres with the Road Engine at the point, a mid train helper and the third at the rear pushing. This way they did not have to stop at Lobato. Also have footage on the first helper at the point with the road engine and the third at the rear just like C&TS' 1992 version.
Kevin