Sans, I'm not getting it. A force is being applied to a structure that is designed to handle the ensuing stress do to cross sectional area and shape. You then remove a piece of that structure with a bullet, the remaining structure can either handle the increased stress or it can't. What does the amount of strain have to do with it? I also don't get your point that thee X-2's system is more highly strained, stressed yes after all that's the point of flap and lead/lag hinges. Not trying to be a prick, just trying to understand you point.
As far as ballistic tolerances planned, I really doubt they have a solid answer to that at this point.