Ok, I checked the harness carefully last night - leads basically run from +-B, ALM, -B, Safe, Ground

The lead coming off the Safe pin is the second 12v power lead - really not necessary. The first power lead comes off of -B (battery?)

The unused pin connectors are: MUTE, CAN+, CAN-

I understand the CAN Low and CAN High leads are attached to the on-board CPU... so is Safe another one of those computer leads or no?

Also, what does +- B stand for? Is this the switched battery lead that isn't supposed to be there?

As ref, from the back, the pins are:

CAN+ +-B
CAN- ALM
MUTE -B
GND Safe