A sensible idea is NOT to run it along the roof or you will wear it if the side curtain airbag goes off. Do as I do and run it along the floor under the door trims and up into the back corner.
When taking the bottom of the wiggle tube just lever the inner end (under the tube) inwards a bit and you will see where it lifts out.. I use two seperate cameras so I only had to run a twinflex to the rear quarter and the original camera cable from there to the camera. If you are using body tools you should be able to get one down behind top of B pillar trim and just feed the cable in as you slide it along from one side to the other
What camera are u fitting. Hope fully not DOD like the OP