Vossy
10+ year member
CarAudio.com Elite
What I did was I lined the part I was sealing covered in tape, made an MDF baffle around the outside for a base seal. Silicone/foamed the outside, another mdf layer to the sides (trunks an odd shape) with spray foam behind it (over more tape) and covered it all off with Alpha Damp so it's a flat surface. And to make it look pretty I sprayed it with black plasti dip. No difference in SPL open or closed anymore.