re judders
Is that where those judders come from. Wow, that is good to know.
Also, Art, what these folks have been saying about putting the new splines right next to the existing ones (holding the shift key, of course) and then finding the right segments to straighten, is exactly right. I'm fairly familiar with the stretch of track you're talking about, having just replaced about half of the mainline track on the Marias Pass layout for track direction. The Sweetgrass line gave me the most scares because of those long curves, but once I found which segment I forgot to straighten it all went back to the the way it was.