I had to replace a rear coax cable on a Blackvue rear camera, and reading up about routing it down the side of the roof lining, and pulling away the trim, I thought it must be easier to run it directly through under the roof lining. I removed the centre light by unclipping the lens, levering up along the front edge of the lens. This exposes the two screws which hold the light in place, once they're removed, pull down on the front edge and pull it down to remove it from the roof lining. It's a similar method to remove the map lights, after removing the screws exposed with the sunglasses holder open.
On the roof lining at the tailgate lip, gently prise off the centre button so the roof lining can be pulled down. I had some 10 sq.mm flexible cable which is stiff enough to push through the gaps, but flexible enough to follow the curves. Wrap tape around the end so it doesn't snag the headlining fabric. I then pushed the cable through the centre roof light aperture until it emerged at the tailgate. I then taped the cam cable to the big cable and pulled it through for the roof light to the tailgate.
I then did the same thing to pull the other end of the cable from the centre roof light to the map lights aperture. From there to the front edge of the roof lining is only a few inches, so it's easy to push the cable plug forwards to emerge behind the rear view mirror, where the front camera is located. Excess coax cable was coiled up and pushed into the space under the roof lining. The light units were then refitted.
The rear camera is attached to the rear screen, so the plug had to be fed through the rubber boot which carries wiring through to the tailgate, which is a tight squeeze considering the bundle of wires already in it. After detaching both ends of the boot from the sheet metal, I passed a length of 1 sq.mm insulated solid copper (stripped from domestic twin and earth cable) pushing it through the boot from the tailgate end. Take care the copper wire doesn't puncture the rubber. When it emerges at the other end, fold the end over around a loop in the coax cable, Pull it back through the boot, drawing the cam cable with it. One side of the loop has the plug on the other end, so gently pull the plug through the boot. A silicone lubricant spray will help it slip through the boot.
