Anyone have advice on finding the correct location for the sun visors before I start cutting the headliner?

do you have a 68 camaro
a 69 camaro
a 70 camaro
a 72 camaro
an 82 camaro?????????????????????

'69 Camaro.

Chris,
Dont you see where the sun visor supports were screwed in through the headliner? The supports were about 1 1/5 inches in from the headliner trim moulding. In both corners. You should see 3 small holes in the headliner.
I hope this helps you as it was a little vague...your question.

No holes in the headliner at all in the corners. This may be a new headliner in the car. It's glued pretty well too so I'm afraid I may tear it if I start to peel it in the corners.
The visor brackets seem like they'd need a fairly large hole for the spring assembly as well. A little gunshy to start poking holes until I know for sure.

There is a clearance hole for the spring assembly with the three mounting holes surrounding them. You could use a sewing needle to locate this hole and then go from there. Maybe there is a car show nearby this weekend with another '69 Camaro for you to look at.

If you don't have your headliner in yet, the easiest way to do it is put the screws in the holes prior to headliner installation. This way you can feel around to find the screw heads, then slice a small X on top of each. Clean, easy, and simple. :)