I have a '92 coupe in which I recently replaced the headliner. The original sound deadener came down like an old asbestos ceiling. I used Dynamat. It worked great. Tap on the roof and it sounds pretty solid. There are other products that are cheaper but I don't know how well they work.

I used dynamat on the ceiling, 100% coverage and as previously stated it is a solid thunk when tapped on. If I had it to do again and I probably will in the future, I would have also used some padded type of material up there too. Reason is that it would help around the edges and the sail panel area to keep it looking snug. Installing glass, mirrors, visors etc... Will cause looseness where you had a nice tight fit.

I too used peel and stick - fatmat then foil backed bubble insulation. No heat from above. Now about that big magnifying glass on the rear - that's another story!