We decided to secure our solar panels inside the custom rails so they are hidden from the casual observer. An added benefit is we can still use the custom rails to secure other gear.
Our wiring enters through the stop light housing to avoid drilling more holes on the roof minimizing the risk of a leak. If you look closely, underneath the panels we added inline fuses for each positive wire. This help protect the system inside the van in the event of a catastrophic shock
Hint: Minimize holes as much as possible
Tip: Solar panels work best when they have good ventilation, so raising the panel a bit will help keep them working at optimal performance.