Ok, now the interesting part.
1. My upshift (cable release) results were much more consistent than my downshift (cable pull at the shifter) results, so I used those.
2. This is done on a 1st gen (silver caps, 2000ish?) 9sp Ultegra STI shifter in sub-par condition.
3. This plot is cable pull between sprockets, so there are only 8 entries for the 9 speeds.
4. My 2 results are in red. Your 2 results are in blue (from your data in post #20).
5. I defined #1 as the large sprocket in the back and #9 as the small one (11 tooth in my case). I think we numbered our data in opposite directions. If this is not the case, then something is off, so please point it out if so.
6. In general our results are very similar. The end values are very different. This makes sense as those positions are controlled by the derailer limit screws, not by the shifters themselves.
7. As suspected, the cable pull per shift is not constant. We know (or at least I strongly suspect) that the sprocket to sprocket spacing is constant, so as a result you can expect derailer ratio to change through its full travel.
