Thanks - that was plan B. With that approach, the tones would be coming out of all the speakers equally, I expected, and with this approach we keep the majority of the tones coming from the rear of the car. There is some PDC tone from the front speakers, not sure why, but the rear speakers seemed louder in my testing.
Both are totally valid approaches as long as everyone understands the implications (with mine, don't center the fader, and with Technics, be aware that the rear bias goes away).
Musicar Northwest Portland OR musicarnw.com
High-performance audio for BMWs