Late last year I was posting about a leak at the back of my truck's shell in this thread.

Since then I discerned by a water test that the seal was failing not between the door and its frame but between the frame and the actual shell, as seen by the gap in this picture:



As opposed to using silicone here, I would like to remove the door frame and restore some kind of water tight seal. This video gives a good overview of removing and replacing the door frame:


However, it does not cover what kind of gasket is necessary between the frame and shell to form a reliable seal. I stopped by a local truck customs spot and they quoted me a little more than $100 with a new seal and rivets. When I asked what material would go between, they showed me something like this:



It looked like your standard open-cell low-density adhesive foam and thought I would check here and ask if this seems right or if there may be something more long lasting. I am thinking this type of material may be chosen over a closed-cell foam because it can be compressed very thin, and when the frame is cinched in place it will end up looking tight and clean.

 

I would revisit the silicone idea...
if you use masking tape you can create nice neat straight clean lines and you won't have to worry about leaks....