Way back when I repaired this trunk lid, I dug out all the original foam that filled the cavity inside the inner frame, especially along the trailing edge. The foam also served to attach the frame and the skin. Now I have an empty cavity, and a gap between the frame and skin.

I did buy some 3M pillar-filling foam as the material closest to the original fill. I know this will make the rear edge of the trunk lid more rigid, and also the skin. But it can increase the chance of water getting trapped.

I am also thinking about using a panel adhesive just along the edges of the frame.

Any ideas?