Pete,

Thanks for the mathematical rule of thumb and especially the point about deviations in real pots. I just wanted to be able to know the resistance value after positioning the pot at various tonal sweet spots so that I can use a fixed-position switch to get the same sound. Since this is for a rear-routed guitar, the simplest thing do to will be to measure it with a DC ohmeter. {Slaps forehead in disbelief.}

-Ben