jason i've read those claims as well yet i and nobody that i know of has actually lost anywhere near that power or fuel economy. average is about 2-3mpg loss if any, and maybe 10-15 lbs/ft of torque lost. you have it right about the methanol and lye, can recover an amount of the methanol (all of it if your patient enough but that could take a few weeks per batch) and the lye is used up in the reaction.

to answer the question about 100 gallons of veggy oil, on average you lose roughly 20% to glycerine so you would get about 80 gallons of fuel and 20 gallons of glycerine.