Brad,
I have been running the O2 sensors for the last two years and I have been reading everything that I can to try and determine what the best A/F might be for my steup on E10. From what I have gathered, there might be a "range" to shoot for and then tweak from there.
Since there are so many variables (outside temperature, octane, compression, timing, altitude, vehicle combo, etc.), I have been testing with 12.5-13.0 WOT A/F's for my WOT range. I do think that the "seat of the pants" shows that 12.8-13.0 feels quicker for my street car.

You will find that there are some people who will aim for 12.0 and some that will aim for 13.4. I was finding so many different opinions on what number to aim for, so I started testing different A/F numbers and found what my car seemed to like. Two years ago I aimed for 12.8-13.2. Last year I aimed for 12.4-12.8. This year I will aim for somewhere in the middle around the 12.8-13.0 range.