I've added it sparingly on mine, at least in some areas, doubled up in others. Even with the trunk divider board in place didn't want any of it visible at any angle. But that rear seat/trunk divider, parcel tray and inner roof panel are all good areas to add some thud to. There's actually a board liner between the roof shell and inner structure, not sure if it breaks down or is too thin but can have extra poked in around edges to stop those layers vibrating as well.