Take a look at my recent thread in the scratch build forum entitled "First Scratch Build". I built a small Ugly Stick off some internet plans, and I built the fuse sides and center wing ribs out of balsa (per the plan). In the last couple of posts, you will see the end result. During a relatively minor bad landing the plane experienced pretty serious structural failure. The balsa just didn't provide the strength where it was needed.

http://www.rcuniverse.com/forum/m_87...tm.htm#9141906

This may not apply directly to your question, but it was a good lesson for me.

Good luck