I don't know if I am doing mine the best way, so if I am not, hopefully someone will correct me.
On the Scamp
16* there is a power converter under the drivers side dinette seat (and in my trailer also a Progressive Industries EMS now).
The converter is plugged in the back of the power distribution center** (or PDC, the thing with the breakers and fuses) which is near the floor under the driver's side cabinet.
Now... on the 12 volt (left) side of the PDC there are fuses that are fed positive voltage on the trailer's front side of the PDC, and on the back on the PDC there are connections for the now fused + 12 VDC. Further to the left, on the back of the PDC, is a buss bar with the white wire ground connection.
In my case there are only three 12 VDC fuses. If I had a furnace
and 12 volt fridge
there would be two more. So what I did was to utilize the two unused 12 VDC circuits (BTW, there are more available but be sure to not exceed the maximum amperage that is available.) I ran two conductor, 14 gauge wire from both the fused positive and ground connections (buss bar) on the back of the PDC. I also anchored the wires since there was no built in strain relief. This way I have both positive and ground straight from the PDC and don't need to worry about picking up a ground or negative somewhere else.
* Not a Parkliner
of course but I doubt there is a great deal of difference.
** Progressive calls it a Power Control Center