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

....you should also consider waterproof "through the deck" wire feed-through fittings (used for marine applications, and can also be used in RV applications):

-right angle feed-through compression-ring housings here-->

....explore these solutions. Far better than drilling a hole in the roof and slopping sealant around the raw "edges" with no restraint.

S-