The BSFC numbers are very consistent and they are a more reliable
   indication of the mixture. The Innovate wide band mixture monitor has
   been a disaster. Unfortunately we found this out after we set
   the mixture based on its erroneous numbers.

Well, BSFC is what you are after anyway. I would be optimizing for BSFC
(at part throttle), and recording mixture strength to use for additional
data analysis. I would not be setting any particular mixture strength.
BTW, you should measure the fuel's specific gravity, and you should be
sure you know if it has any oxygenate additives (ethanol, MTBE, etc.) It
may be important to understand how the engine behaves with any of these
additives, and make sure the calibration works with any fuel you might
normally encounter.

Jon