it will be less metal because you get more room before hitting the maxxed out volume. that means you get a slightly hotter and less compressed tone. but palm muted chunks will be less consistent. a little more passive the description i frequently hear.
Interesting, where would you put the second battery? Someone was selling a kit a while back that looked real easy and removing one battery would still give normal operation.
Never did it with a luke but did it with my old LP and Ib7 string. And yes there was more headroom and slightly more sustain. And the pickups did sound warmer and more passive. But I used these batteries......
Thos are the things I have heard too what IU really wonder is what does it do to the single coil pickups. I know people who have done it but they all used HH pickup configs. The cingle coils should be a whole diff monster.
The second battery would go into the control cavity.