Brett,
I'd be interested in whatever you might come up with. I'm intrigued by the 1947-1961 period at S. Baker. Relatively recent history, but not much was documented.
Delving back into my undependable memory, I recall mention of shay #7 in a "Trains" article, it might have been a sidebar to a piece on the Hesston museum. Some time around 1980. The author claimed it had seen "occasional" use as backup for #101 until the end of operations in 1961. Don't recall who wrote it, but would be interesting to know where the information came from. If the 1.5 mile remnant SV was busy enough to justify keeping backup power around it would shed some interesting light on latter-day operations.
I've always wondered if the last 3-rail operations were just switching standard-gauge cars in & out with the ng locomotives as most seem to think, or if the narrow gauge saw use as an internal tramway for the mill complex.
And we still have no idea when Whitcomb #100 left the property.....
J