Some installation tricks
On some class B conversions, sometimes the easiest place to connect to the battery is right at the fuse panel. You can backfeed a solar controller through an unused fuse, which accomplishes two things: 1) It's easier to get to from inside the vehicle. 2) it provides the necessary inline fuse. 3) It already has a large gauge wire going from the fuse panel to the battery.
Just don't make the mistake of placing the solar charge controller too far from the fuse block or battery. The controller needs to know the battery voltage, and any voltage drop on the wire effectively subtracts from the voltage the controller puts out getting to the battery. Either put the charge controller very close to the battery, or use large gauge wire (6 AWG or better).
Another trick I've used on fiberglass tops, since they are already an insulator, is to cut the wires from the solar panels where they're going through the roof, crimp ring terminals to the ends, and reconnect them with a stainless steel bolt. I apply a sealant before tightening the bolt and it's a mechanically strong and water tight connection.