I didn't use a fixed mount so I"m not sure. I had the camera on my helmet, facing backward, and slowly turned my head as the rider went from one side to the other.
I think the wide angle with a stationary mount would keep the rider in frame, maybe the medium, but definately the narrow setting would be too narrow with the camera in a fixed position. This was just an experiment to see how the three settings would compare. Even the narrow setting is too wide for a good view of the rider.
Unfortunately the narrow FOV is as close to a zoom as the GoPro will deliver.
Below is a link to the video shot in narrow angle. The rider is my buddy Ronnie B., 56 years old, working on some new surface tricks. You won't see any ollies, shovits or kickflips, but I think he does pretty good for his age.