Matt,
I am curious to know just how many people are breaking their Impact fuselages in flight. Can you be certain that these failures were not due to some other contributing factor? (e.g. improperly installed bulkhead, rudder post or stab tube? or possibly prior damage?)
I know of several Imacts that have had no trouble (one doesn't even have the rear bulkhead installed!) and these guys are flying them hard, even surviving the Reverse Avalanche in Masters '05[:@]

I realize that you can fly a plane hard enough to break it, but that is certainly not going to happen flying the sequences with proper throttle management and smooth inputs. Unless there is a manufacturing defect, I find it hard to believe that the Impact fuses are suffering compression buckling due to flight loads....Is this the type of failure that you see happening?

As you know, it is easy to build a model that is strong enough....however, in pattern, we always strive for a model that is JUST strong enough. From what I have seen, the Impact meets this requirement without significant "sturctural" modification.

If it turns out that there really is a structural problem then this needs to be communicated to every Impact owner....and then it would be wise for Comp-ARF should issue some "AD" to correct the problem. As I said, I am interested in seeing the data...how many are failing?, what are the conditions causing the failures?, are there any "common denominators" that stick out?....e.g. production batch number, Engine/mount choice (i.e vibration problem), etc.?