rcamacho,
I went with a 70 or 80 mil butyl rubber, foil backed mat. roll it on with a small wooden roller after cleaning the surfaces good and degreasing.
I used a black colored foil for the floor since some will be exposed at places I don't have black carpet, which came out pretty decent.
all the carpet and insulation was completed previously, so I only have replace the original foil/bubble wrap insulation at the front seats forward and all foot well areas so far, and the entire roof.(which is a one piece custom aluminum sheet).
the sun still makes it pretty warm to the touch, even with the carpet headliner on, but it is a gun metal gray surface so it will be hot no matter what.
As far as the sound it is no longer like driving an empty beer can down the road. knocking on the side of the foot well is definitely more solid.