Arup, on a control line model you'll automatically and unconciously select the amount of up elevator needed to fly level in any event  So your model will not truly be flying at an actual 0-0-0.  It'll be 0-0-x due to the slight up trim needed to hold level flight.  Only during the vertical parts of squares and wingovers will it truly be 0-0-0 when the model is pointed straight up or down.