After doing a bit of sketching of possible geography and a rail route through such, I've revised the gradient profile to better reflect what I was intending when I wrote the posting for the run along the line. Attached is version 2 of the profile, now somewhat modified from version 1. I've put in marks on the profile itself for the mileposts, with their heights in brackets. The beauty of the way I've set up the code is that I can add and remove such markings for features just by modifying a variable!