3M 77 is not cheap. Elmers spray glue is about 1/3 the price. I've also heard stories about spray glues delaminating. I don't build with foam, but when I did I used Southern Sorgham. Is that the stuff Dave Brown markets?

If I were to build with foam again I would use polyurethane adhesive (gorilla glue, pro bond, etc.) but not spray glue. I just don't trust the stuff. I use it around the shop for non-critical type things and it tends to harden and crumble after a year or so.

On the other hand, if you're like me and your planes only last a couple months, then it's never really an issue.