Well I definitly found a good part of the problem....the box has a .5cm gap right near the top. F**k I am lazy sometimes. Anyways, the big problem with getting this box sealed is that it is below the parcel lid in my benz and is in super tight clearance with the gas tank. The sheet metal had to be uncurled then bent to fit the sub properly. THis means that the fitment is even harder. So I am going to go get a big tube of silicone and just silicone hte crap out of it until it seals properly. Still wondering about the polyfill....do you fill the whole box with the stuff or just the bottom of it? and what will it be called at wal-mart?