Today I repeated my rides of September 4, trying to be steadier on the very steep portions. I’m not sure I succeeded. The riding on the section A-B has a lot of variation. On the uphill I am in a very low gear, pedaling fast to maintain slow progress and trying not to wobble. On the downhill I am coasting while riding the rear brake.
I did incorporate two two-way rides of the mid-course hill, which is not steep, having an elevation change of 33 feet over its 1.08 km length. The two rides agreed just fine, just as Neville’s did. Intuition leads me to believe that this indicates that a modest hill in the calibration course has little effect, so long as it is ridden both ways. But intuition is not proof.
Still, even with the ridiculous incline of portion A-B, the error would be well within the SCPF, and it’s likely that more humane inclines would have even less effect.
Anybody wishing the raw data, just say so and I'll send you an excel file to play with.