That's what it feels like, panning with a 600mm lens following an accelerating sports prototype up hill towards me. How late dare I release the shutter?
As the car gets closer the panning speed increases, as the angle changes more rapidly the closer the car comes to me. I know at some point I'm not going to be able to follow the car as it will go by too fast.
It's a matter of nerve, relaxing and panning smoothly while the car speeds closer ...