Plain and simple, I needed 12v / USB power ports near my rear cargo door bar light to power some LED RGB light strips for ambient lighting. The solutiuon was simple.
First, get panel mount 12v dual USB charging port panel.
https://amzn.to/499kvkI
Second pull the header panel over the rear cargo doors.
Third allowing enough space to be able to operate the switches, and drill a 3/8" hole to pass through the wires, wallow this out a bit as it will be snug.
Fourth extend the wires on the USB panel, I soldered some 12ga on and heat shrunk insulated the joints. About 8" of wire for both hot and ground.
Fifth pull the circuit fuse for the drivers side as this is the fuse for this circuit on my van.
Sixth, using a 10-12ga straddle tap connector, make hot to hot, ground to ground.
Seventh Replace the fuse.
Eight test.
Ninth, be happy with the results.
I have a package of 3 more of these ports, I will be adding these to the passenger side by the factory 12v power outlet to allow me to use them for charging devices. I need to figure out how the side panel is installed / how to remove it to do my install.