Just to clarify, Balance means left to right. In 99% of cases, you want it right in the middle. Unless your normal seating is too close to one speaker, and too far from the other.
FADE, on the other hand, is front to rear. Whatever balance you have dialed in, should stay in place. We use the following FADE: All the way one way or the other for inside or outside. In the middle when we want the same sound both places (unusual) or slight signal on the inside, so we know what's playing on the outside, without disturbing cabin occupants.
Be advised, manufacturing techs don't understand this at all. It is very common to get a TT wired so that Inside and Outside speakers are wired as Left and Right. If you find that Balance moves the sound in and out, then it must be re-wired. (easy job at back of radio, but only if you know what you're doing) To hear only one channel of a stereo source is just plain wrong, and will sound bad.
Marty and Martha
2015 Z-1 211RD
2012 Nissan Titan