Okay, yes, that's true. The "neutral" conductor will carry the current of both halves of the circuit if wired that way. Howeever, when it was mentioned that #8 was used, I hadn't envisioned its capacity to be taxed.
At 12 volts, 300 watts is 25 amps. 50 amps would be a stretch for #8, but I can't imagine the two halves of the circuit being loaded to capacity. I concede that, in theory, polarity does matter, but not for functionality.
