A nearby bodyshop uses a product called "wax-oil". It is sort of like the spray foam stuff used for sealing drafty windows and walls in your house. They put an extension tube on the wax-oil can and use it to fill the rocker panels and door bottoms. Sorry I don't have pics, perhaps someone else does?
No, we were reffering to this one quoted above.
I would never put some kind of foamy element inside the rockers!!! I bet it would make things worse!!!
