Nice looking, sober mod with a couple of minor flaws or inconveniences:
Has a loose button. Doesn't misfire but is loose.
Potentiometer is difficult to read and adjust. Also 0 isn't 2 like mentioned. More like 3 or even more. For this particular mod, 0 is app 3v and 100 6v.
The parallel/ double series configuration takes 10 min to fully understand.
But it's a hard hitter and works well. Woud buy again.