Obviously, if you want to put in a sound deadener of some kind, now is the time to do it. If it's a good quality jute pad, you don't have to add anything else as far as padding. If it lays flat, you don't need to glue the whole thing down, but on trouble spots like next to the trans. tunnel, you might want to glue it.
No one lives forever, the trick is creating something that will.