Clamsmasha, it works and it is practical, but it is not as strong as a thin layer. The "foamy" part is not very strong, what "shi thouse" was looking for.
E.g: "Parts being glued with polyurethane needs to have a tight fit to be strongly joined. polyurethane is not a good gap filler. Although it is sometimes advertised as gap filling, tests show that strength is reduced when the glue line is thick. When setting it froths up and the froth, although gap filling, is not strong."
www.christinedemerchant.com/adhesive-glue-polyurethane.htmlOr he could just use epoxy, but it will harder to remove if needed.