1. black hotwires and white common wires coming from the base and from the cable; by design...

2. I need to get connector for this knockout hole that cable is going thru...
There is a connector that twists on the cable and compresses/pops into hole.

3. I'm using red and yellow wirenuts, just like the other end inside junction box...twist wire nuts on cable ends and, push into box and cover...

4. Like I said, this is common supplies, so I used the same screw, nuts, as earlier(base/box) to attach metal strapping for a hanger and put it right about the middle of the whole contraption.
It seemed to balance well...I attached one to the other end also, just in case...

5. Fasten flexcable to with Zip ties to counter balance arm and hang... cont'd

Great timing, Rasta...I did not order vented ballast box(should have). In answer to your question...You can have the ballast sitting open; as long as it is in a secure place...THIS is NOT as SAFE as placing it in a metal box, but in my case, no-one is going to knock it around...I think I am going to fabricate/find a big metal box...like commercial juntion box and put all my big electronics on/in outer wall. Then I can service it easier and I won't have to worry about heat in the growroom...cont'd