We have been using the new ArcCheck model with SNC 6.6.2 and our pass rates seem to be somewhat lower than the pass rates when using the old ArcCheck model. We have noticed a difference in our dose calibration factors when we calibrate at max dose rate vs half dose rate. Has anyone had this experience? Our results with VMAT plans have been quite inconsistent. Has anyone done any verification as to which model (old vs new) is more accurate?