Pretty darn good! Thats one fast dog and I see how you could loose the point of interest as the dog darts side to side. Perhaps the GRID setting could be used in the DJI GO app. to help keep the subject in the center of the grid.
I'll have to investigate that. By my own admission I haven't looked too much into it all. I just flew by the seat of my pants for want of a better expression
Looks good training ground - I ise a similar area for training labs - good use of the drone to see how the dog responds at distance - will give it a try