Re: Double Heading up Marshall Pass?

The prohibition on doubleheading on Marshall Pass was only on the Salida side. Alamosa Division Timetable No. 125, June 1, 1949. Sorry for the confusion.
With regard to Chama-Durango, my guess is you are right, the up and down profile was not conducive to anything other than putting helpers on the point. My personal experience only goes back to 1960. But I never saw a helper anywhere but on the headend of the train, in either direction, between Durango and Chama. Lord knows what might have happened before that....there tends to be a prototype for anything.
From various pictures I have seen, apparently the way helpers were used between Chama and Cumbres varied. My guess is that after the heavy pipe movements began around 1950 they experimented a bit to figure out how to minimize pulled drawbars and broken knuckles, etc. But except on three engine trains, I have never seen doubleheading on freights. Of course the San Juan doubleheaded when it needed a helper. But the rule about a prototype for everything applies here as well, I'm sure at one time or another, for reasons good and bad, one of every thing happended at least once.