Brock,
I don't recall the exact size except that I bought the longest screws I could get at my local Ace. I'm thinking #8 screws with washers and 1-1/2" to 1-3/4" maybe even 2" long since the distance through the roof, insulation and headliner was at least an inch and then there was the Go power box thickness on top of that. I recall the holes in the go-power box were larger than I wanted to use so I used washers with a smaller hole so I could use a smaller screw.
I recall measuring the distance from the headliner to the roof skin once I cut out a path through the insulation for the wiring. I'll see if I can find that info. I tried to document it well so I could write all the final details up (which I have never done).
Regards,
Craig
