You're welcome to any of the resources in my InsightTech folder:
https://drive.google.com/open?id=0B4...jd5amdITThsb2s
See folder "Honda-Insight-2000-2006", wiring.
On page 58, the wire from the VSS is shown to split to both the ECU and cluster, so you should be able to fool the ECU without causing the speed displayed to change. It is also shown to go to the TCM (presumably in CVT models, as I don't think the MT would have one) on page 36.
The variables that initiate auto-stop seem to vary, to some degree. For instance, sometimes auto-stop doesn't engage until around 12mph, if I haven't gone over perhaps 25mph - that is, I can speed up to ~21, then slow down to 19 again, and auto-stop won't engage. I haven't paid close enough attention to it to understand exactly what's going on. I'm inclined to believe you can solve this with some trial and error.
A related idea came to me while reading this thread; I assume MPG calculations are done in the cluster and are independent of the ECU, so you could send whatever signal you wanted to it and not mess up the gauges. Engine idle speed (for instance when in neutral or changing gears) varies while rolling. Above ~51mph, the engine revs to about 1300-1400rpm and begins charging with 4 bars. It would presumably be possible to initiate (or prevent) this with the same device.
