The air box I got from Jabiru was open on the back side, I guess it's supposed to go on a flat surface. Since the S19 firewall has bumps in it I had to make a back cover. I thought about fiberglass but decided to cut a piece of aluimum and rivet it on. Sealed it with silicone and riveted together. Located it on the fire wall then drilled 4 holes for mounting. Located the carb heat cable location and drilled. Installed box with 2 washers under each bolt for clearance on firewall. Routed carb heat cable.