I'm framing in a newly installed gas fireplace and when I went to attach the top plates to the rafters in the ceiling, I discovered that the ceiling had acutally been dropped about 4 inches! So there is half inch drywall - 2 inches or so airspace, old quarter inch drywall and then ceiling joists.
Do I just rely on the drywall and forget it? Should I use construction adhesive to attach the top plate to the ceiling? Use 7+ inch screws to get to the ceiling joists? Cut out the dropped ceiling(gawd, please no!)and bring the framing up to the old ceiling? The frame is basically a three sided box 2 feet deep, 4 feet wide and 8 feet high.

thanks all