I don't know, but you might end up with more of a mess than you started with. I have used the stuff ( urethane foam) to manufacture odd shaped cabinet and furniture shapes that were too costly to make from wood, and it required some pretty stiff molds to effectively contain it. Have also used it around new windows installs, and seen it blow out the front and back of moldings when a little too much was used. You could find a lot of weak spots that you did not know you had. The old fiberglass/polyester resins and bondo repairs might be in order.

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'94 940 150k, '86 240 170k, '72 142 KIA, '70 144 KIA, '69 144 RIP