I have been out of the game for a few years but I finally got tired of sitting around and started doing an spl build in a 92 mazda 323. I just laid 4 layers of mat from the b pillar back. I am looking to fill in the cavities and right now I am planning on using expanding foam. since I've been out I want other opinions (I don't want to skimp) I am a privateer so I am using my own money and don't want to use concrete. I am trying to stay in a lower class. Thanks for all the input.