Maybe this is why one of my favorite car's had dash mounted off axis 6.5" drivers and on axis tweeters. The midbass both provided direct off axis sound, and indirect (reflected) on axis sound. Soundstage was high, and everything sounded real. Voices had depth, and an impressive staging presence.
This same car BTW had no rear fill.
That's an idea I had wanted to try and implement. I think it would work very well without any need for "fill". Nice to see somebody's already been there
This whole issue with stock locations might force me to end up 3-way + sub.