I’ve been testing my somewhat "under-engineered" traverser, and made a little video to show it in operation.
It continues to work well, and I now have some faith in the basic concept. I’m in the process of re-enforcing how the tubes are fixed in the foamboard, but that is more of a pre-emptive move than a result of any actual problems so far. The running is smoother than rendered by the video.
PS: I’m aware of the period inconsistency between loco and wagons, it's all still a work in progress