I recently purchased an Art-Tech Corsiar. Unfortunately, it flies terribly. The model constantly pitches up, and consequently, will not fly straight. I have read other posts decribing this model as "flying on rails." Nitro Hobbies sent a replacement elevator set, but this has not helped. Also, Ntro Models tech support sugges that I trim the model by adjusting the length of the control rods, but this does not help. Does anyone have answers?