another thought is i used polyurethane glue to attach the balsa skins to the foam cores. incredibly strong results. i used a foam roller and rolled the glue from a paper plate and applied it on the foam cores. you can literally push/roll the glue around until you have a shiny, very thin sheen on the cores. then i lightly misted the balsa with water, applied the skins and weighted heavily for 24 hours. a rock solid result was achieved. i am very happy with the results.

david