The 19 has never been over 20mph while under power while working on the C&TS. If the shunt/transition/whateveryoucallit doesn't happen until 20-25, it never does anything. Why take the chance of screwing something else up in its removal?
According to FRA regs, if #19 exceeds 20 mph, it has to have ditch lights. The current max speed is 22 in the first 6 miles out of Antonito. At speeds above 20 the 19 starts a real annoying bouncing up and down. I don't recommend going any faster than that.
It seemed to me that 19 runs out of poop pulling above 12 mph, like modern diesels do if they won't transition. My thinking (remember I know just a bout as much about diesels as I do about computers - which is VERY little) if the shunt happened at a lower speed, you'd get more top speed out of it.
The perfect analogy is "hooking up" a steam locomotive as it runs faster.
Of course all of this is mute if we can't get the damn thing out of engine house!!