Quite new to the Phantom world having bought a P2 about a month ago. In the manual it says not to use the Alti switch as this is for advance flyers using Naza which Google shows me to be an upgraded 'brain' for the Phantom. What does this give that the off the shelf Phantom lacks? I am more than happy with the existing performance of the P2 but curious to learn a bit more. Is it more for pilots that fly without GPS enabled?