Remove what you have and replace with something similar. These pads can be bought in packs from restoration companies. In this case maybe VP has it too. If you need to glue it on make sure the glue can withstand a lot of heat. The roof gets very hot in the sun. Definitely don't leave the roof bare as it will drum with vibration. All sound deadening is good and you don't need to cover all of the surfaces. That can get expensive if you use something like Dynamat. Go ahead if you can afford it but the law of diminishing returns applies.