Package tray installation

I once had to do welding on a car with Dynamat what a mess trying to remove it. I couldn't get it all off and what was left still caught fire.
Its good to cover up floor patches to make it look good before carpet. If you can cut it and fit it without the adhesion it would be great. But if you plan on keeping the car and doing future repairs if something happens I would stay away from it . I won't do collision repairs or rust repairs on cars that have it applied. Throw it on a fire and see what happens.