Will,
This might be the hard way, but it worked for me. I bought six 1" screws that fit the sun visor holes in the roof. I cut the tops off the screws, ground a rounded point on the top of each screw, and cut (with a Dremel Tool) a slot in the top of each screw (a screw driver slot).
I then screwed them into the mounting holes, allowing them to sit "proud" (outwards) for about 1/4". The headliner was then dry-fitted into place and pressed against the screw heads. After removing the headliner, it was an easy matter of drilling the three holes on each side and placing of larger hole between the screw holes. This technique has worked fine for me (and, I have gotten three uses out of that set of "fitting" screws.
Tim
