Exactly what
smedsky said, make sure your joint it tight when using this type of adhesive. A loose joint filled with glue is never good, Poly or Epoxy. Poly is great stuff, but I always keep the epoxy around especially for when I Join an ARF wing, etc where you have a larger than normal gap. You can use it on your Cub, because you can clamp the joint. Good Luck, Happy Building.
ORIGINAL: smedsky
My advice is to be careful with a joint that is less than tight. Gorilla glue is great stuff for many things, but remember that the foam is a large percentage of air and last I checked, air is not the strongest adhesive. Just be careful.