Geistware,
Another thing that I found that can happen is flexing of the tail surfaces. I had a real bad pitch couple and loss of rudder authority at extreme rudder applications that was greatly helped by flying wires. You might give that a look too.
I landed one plane that seemed to have suddenly lost rudder authority and trim and found that the vertical stab was broken and one 1/4" stick and the Monocote was the only thing holding it together. It was a miracle I didn't loose it. One good vertical downline would have done it in! I have also used carbon fiber laminates on planes that I didn't want flying wires. The only downside to the laminates is that they must follow the understructure for maximum benefit. If you run them over large areas of open sheeting they flex in compression and cause stress risers that can crack the sheeting.