generally, when i play a scale in one position, i like to keep my thumb in one spot but in the middle of the neck in order to get leverage over the strings.
this allows me to play any guitar, no matter the neck size or the action of the strings. It also lets me treat an acoustic guitar the same as an electric guitar, allowing me to play the same "electrical riffs" on an acoustic guitar. Plus it is a lot easier to solo on an acoustic guitar using this method.
fatcat
