Stephen, when you write that Zone System speed point falls 2/3 stops below the ISO speedpoint, do you mean it is below 0.1 fb+f? Also, I wonder if the WBM choice of 0.17 as the speedpoint means that its CIs are, in essence, no longer comparable to ISO CIs.
On another note, I am finding all the contributions on this thread very informative, thank you everyone. I am not sure, however, as to the best way to interpret my results to find the development times. I realise that one can take great pictures without any of this, but I would love to know my personal timings for N-1, N, and N+1. Perhaps I need to contact the tablet for the curves, and to perform a separate EI test in natural light using a non-uniform target and my camera.