Anybody fill the area between the trunk / fenders?

Use a seam sealer if you're gonna use anything for sealing seams. Down in that area, I would recommend 3M's Rust Fighter. Spays in with a wand in tight spots, never dries and has the consistency of petroleum jelly. Slide in the wand from the top and from the body plug on the inside of the extension panel.

Good luck. and I agree.........find a new body guy. Foam is horrible.