It was much easier and safer to run an extra train as a section rather than as an extra, especially with extra's(Locals) and work extra's(stone trains and m of w trains) on the road also.
As for superior trains such as No. 71 "normally holding the main on meets", as Ron explained in another thread, nothing in railroading was normal. Many thoughts went into dispatchers thinking about which train would hold the main besides which train was superior by timetable direction. No. 70 and 71 meeting at Ames is a good example. No. 71 would almost always be instructed to take siding because the operator would head 71 into the siding and the south switch was a spring switch so No. 71 could pull through the siding without ever stopping, provided No. 70 was already there. Especially at night with few operators working, the dispatcher had to set the meets up well in advance. Sometimes one train would have to stop for a problem or red signal at an interlocking causing a train which was suppose to hold the main on a meet to arrive at the siding first. Occasionally that train would converse with the other and pull into the siding. The dispatcher wouldn't necessarily know of it. Also, even though No. 5 and 6 were first class trains many times the dispatcher had them take siding on meets. And the dispatcher could run a freight train on No. 5 and 6's schedule if he wished. Rick