OFFBOARD control on fixed-wing

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Hi, I need an advice how to implement offboard control in right way. I have a fixed-wing drone based on NAVIO2. I have already implement an object detection on it and it seems that it works great. My task is that I want to mark some object during flight and commanding drone to flight directly to the object if I unmark it drone returns to manual mode. I need to manage pitch and roll. I did it with RC override but I know that it’s bad way. Please give me some advice how to do it right. My system is - NAVIO2 with ROS kinetic and mavros.