I sent you some stuff on this in answer to your PM, but in general you can run significantly leaner with adequate ADI ( sorry guys I prefer the air craft term of antidetonation injection because mixtures of water and alcohol can vary so much from user to user and folks seldom run just pure water).
If you have a quality AFR meter, then I would suggest you get a good max power tune dry and then add the ADI and see how the meter records the change in AFR. Then try a couple different mixtures of water and methanol, and see what happens.
I have seen some debate on how a meter will be effected but I have not seen anyone actually get experimental data.
You may not be able to get absolute fuel air ratios but if you know how much it is effected by the injectant mix you run you should be close enough for tuning purposes.
You may also want to touch base with the guys at RBRacing.
http://www.rbracing-rsr.com/bonneville2.htm
They seem to know what they are doing with this sort of thing.
Larry