If the nutserts are spinning, will they fall inside the roof if the screws are cut or do they have a flange that keeps them from falling in? I don't want to drop them inside and have them rattling around and I sure don't want to pull my headliner to deal with it.
They will drop in like a large version of a drilled rivet would. I have some in mine someplace but the insulation has trapped them. I haven't worried about it.