RE: Deception Rescue
Expanding foam was my first thought too. Not being an expert on the subject though, I would first want to know what kind of density it has. My recollection is that it is pretty dense stuff. You might want to check on the weight first. You might add several ounces to the wing panel (only one if the photos tell the story). But I suppose it's going to be better than a glue mix.
Another idea might be white foam crumbles, microballoons and just enough glue to hold it together. Although I haven't used polyurethane glue (yet), I'm under the impression that it is hard to cut/sand.
Looking forward to this one. I'm working on my D15 fuse sides and formers at the moment.
David.