I decided I wanted something for insulation on the floor. And something that does both heat/cold insulation and sound damping.
I bpught the closed cell foam from Aircraft Spruce. I did NOT get the sticky back. I want to be able to pull it out easily. So I cut it oversized and stuffed it into place. It seems pretty cool like it will do both insulate from outside air temperature and dampen noise. I used inch thick. It doesn't weigh much and I think it will help stop vibration noise and insulate.