Regarding the use of the 7-pin, you can definitely do that from what I've read.
I have a 4 pin and a 7 pin on the rear of my 370XL. I ran the two wire cable under the 370 before I found/figured out the tow brake wires behind the dash.
Then it worked out anyways because the light system in my Saturn Vue is tricky given daytime running lamps and such. I would have been in diode hell.
So to keep things simple I use the 4-pin connector to run to a set of magnetic lights on top of Saturn.
The UTB is VERY nice.. worth every penny.