Bob, I look forward to seeing your results. These three cars have long caught my eye, with the rounded corner doors extending into the letterboard.
What with three similar cars, they were more frequently seen on trains too. 13 was truly the oddball, and yet it is the survivor.
Photos indicate that the C&S appears not to have always turned the mail and express car at the end of the run. While one would expect the mail compartment to run adjacent to the locomotive, many images show the baggage section forward. So, if your pike lacks a wye at one or both ends, that is okay--no need to turn the mail car!
Keith Hayes
Leadville in Sn3