I think the c-19 are underrated in those time tables. But they say a c-19 is rated for 92 tons on 4% like on the RGS Ridgway to Dallas Divide. On the south end Durango to Cima summit at 2.5% they are rated at 185tons.
Now going of of pictures I have seen of RGS 40 and 41 it would seem they could pull about 6 cars up 4%, and double that on 2% or 2.5%. There is a picture of 41 pulling 11 cars, ten boxcars and long caboose 0404. Going off of the light weights of the cars that's 127.65 tons. If they were all loaded they would exceed 300 tons, so they must be empty.
These trains going up grade would be wide open throttle and be moving between 6-12mph. Down grade could be the same or faster if he was brave enough.
They would be stopping at every tank up grade. They were about every ten miles. Coal now thats a different story and can change for different firemen. Some were better than others.