Your choice to use a fixed bottom reference is really interesting to me conceptually in the context of the thoughts I started the thread with. It seems to me to be an indicator of the "negative centric" thought that the pervades much of technical photographic discussion. Maybe a bit of an arbitrary quest for minimum exposure. This is technically a reasonable, simple, measurable, line of thought and technical discussions benefit from common reference points, but that does not necessarily translate into an artistic advantage.
I see Adams' intellectual conundrum reflected in your choice. On one hand Adams is trying to get people to visualize in the scene what they want on paper (essentially ignoring the negative), on the other hand Adams is trying to get us from A to B within the constraints of the available materials and tools of his day. Fixing the shadow point simplifies the discussion, but it's not the only, nor even the best way to take every photo.
For example Jose Villa http://josevillablog.com/ has an interesting style that looks to be using flare and the upper reaches of the film curve decidedly to his advantage. From interviews I've seen and articles about him his self described shooting style is obviously into what I would classify as the extra exposure range on his favorite Fuji 400h. He shoots it at an EI between 200 and 25, all done specifically for effect, this style places the toe of the film is so far outside the print range that it's shape and exact placement is essentially irrelevant to the end result.