Working through my Model 3 Premium audio upgrade. There is a lot of discussion/advice about where to get your turn-on signal for your after market amp, but I'm not sold on running a line all the way from the front of the car (VC left or cigarette socket). I haven't seen anyone mention using the red wire that powers the existing rear amp. I've tested that it turns on 4-5s after the big battery, which seems ideal. And it's so conveniently located. Is there any reason people aren't / I shouldn't use this as the signal to switch my power relay?