Well i tried it and it's a no go for me.
Installed a 1meg pot, tied one side to constant power other side to ground, moved the wire on the Z2 to the secret location, set the center pin to 2.5 volts, unplugged my VSS from the z2, reset unit.
It works until the unit figures out where it is and as soon as it does i get the parking brake improperly connected and then it shuts off the video. I experimented a bit with the voltage but couldn't get it any better. It does delay the video over ride a bit with all this connected but video only stays on for a mile or 2. Let me know if there is anything