I don't know if any cursus goes uphill, but I'm sure that Terry will. There doesn't seem to be much literature about cursus and the only way to begin to understand them would be to plot each one noting direction, length, gradients (the massive Dorset one goes up hill and down dale) and possibly proximity to water, long barrows and settlements. Then ask the question: What do they have in common?
I know that the Dorset cursus has later barrows associated and I believe that one of the Thornborough henges is constructed over a cursus. Someone on the Portal did a longitudinal survey of the Dorset(?) cursus giving heights etc. I'll see if I can trace it.