We had complete access to the roof without having to remove the headliner. We had to examine the console to see how close to the roof the contents came. We needed vertical space for the NMO mount and cable. You do want symmetry when you install the antenna. We measured between the roof beams and marked the spot for the hole.
Pilot holes are always a good idea.
We went up from the inside. Greg let me make the first pass to see if I was really serious. I figured if I slipped going up with the pilot hole no one would notice. As it turned out this small pilot went through quickly and easily. The next step was to insert a piece of cardboard under the headliner so the hot metal shavings would not fall on my leather seats when we came through the top with the larger drill bit.