Headliner mounted DVD player

[MiamiVice]

I had my Sony DVD player mounted in the headliner w/ its metal mounting plate in place of the dome light. I have a 2006 H2 SUT with a sunroof and the problem is the DVD player shakes and pops out the headliner buttons at the opening of the sunroof. I purchased bigger (fatter) buttons and forced them into the holes to hold up the headliner. What buttons, screws, or fasteners are people using to hold up the headliner.