RE: using expanding foam in built up wings
You might want to consider the amount of weight you would be adding, too. Though it is foam, it is much heavier foam than that used to make foam wings. And if you put it in one wing only, you will need to add about the same amount of weight to the other side. I saw a trainer which someone had used this stuff to reinforce the firewall and it was very heavy in the nose. Not a big problem with the trainer, I suppose, but you might not want the added baggage, especially out on the wing tips. Rebuilding the wing is not as big an issue as you might think; and it is a better option IMHO because you will be able to see ALL the damage that needs to be dealt with. Good luck, Dzl