Another Focus specific audio question

[Tj-zetec]

I know i'm pushing the borderline here but i thought I'd ask here first seeing as the audio forum is mostly falcon owners.

the focus (namely the 6000 unit in the LR) has, as far as i've been informed, two earth wires (two wires supposedly going to earth to word it better)

I know a few of you here have installed decks yourselves and I'm interested to know what you've done in this case.

According to the "diagram" i got here at focusfanatics they're the black with green trace and black with yellow trace. Both are situated in the same plug.

What's the go?, is one unused, to they both ground to the chassis? am i better connecting it directly to the chassis? am i asking too many questions? :

Also, on that american diagram, there is only one connection on the harness 3, which is the one going to the speed sensor (i don't use [hate] the avc and therefore have no intention on using it even if it is possible)
But on my plug there's a couple of wires. What are they?

i have a few more questions but they're purely audio forum so i wont bug you with em.

Hooray for more amature auto-electronics!