12 seems to be my limit, lol. Life drain speed could be proportional to the tempo, otherwise it becomes insurmountable at slower tempos. Power drain could be paused during the cue-read phases too, otherwise you end up in situations where your power just drains to zero while you're unable to input anything.
I keep playing it, it is fun and it IS hell. I've learned I'm good at keeping tempo with quintets and okay with nonets, but heptads cause suffering