Next, “eye up” where its going to go, preferably with solar panel spoiler pointing to the front of the caravan/motorhome. Keep in mind when positioning it where you want the cable to pass through the roof, this would normally be into a wardrobe area or top locker or to a known pre-wired solar panel connecting point if you caravan/motorhome has one.
Measure from the side of the van to make sure the panel is straight and then mark with a pencil so you know where to put it when the sealant has been applied.
The shorter the cable run the better as the shorter cables will give less resistance and less voltage drop.