Dane - I'd say it would be effective at that. No doubt sealed in all that lost pocket change and chunks of rust!
Mat - it was a dump bed truck that sustained some major damage but I didn't look close enough to see how. That was only the tip of the foamberg. To rockers panel was filled and I think the passenger door didn't escape either.
Good question about the bondo
Around here I see quite a few trucks that have the rocker panels filled with foam. Can't imagine it does much but trap moisture in there.
Scott
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Camano' 1986 F250 Supercab XLT Lariat 460/C6
'Chanute' 1980 F350 C&C 400/NP 435 - Gin Pole
But there ain't nothin' wrong with the radio