I used lizard skin ceramic spray-on insulation underneath the lizard skin sound control. Eastwoods carries both, I bought mine at Carlisle a few years ago. Can't give you a report on the insulation properties but if it is anywhere close to the sound control properties I'll be happy. Rap a knuckle on the roof and it goes thunk - no ringing at all. I had enough ceramic to do the roof and firewall/metal floor of the burb with enough left over to do the roof of my 64 Camino.
