About to drill through the roof to mount solar panels- tips?

I mounted my 120W solar panel with Z-brackets and rivet nuts into the aluminum box tubing under the skin. The wiring went into a PVC LB fitting inserted into a hole drilled through the roof. There was no refrigerator vent on my TC since it's a pop-up.
Everything was liberally coated with Dicor afterwords and the LB fitting completely filled with Dicor.

I haven't had a leak since installed in 2005.