Using a video camera set at 30 frames per second and attempting to start several times on the mag I calculated the approximate speed required to start on the mag.

The results:

19.5 degrees in 1 frame = 97.5 RPM NO start
20.5 degrees in 1 frame = 102.5 RPM NO start
23 degrees in 1 frame = 115 RPM Start
24 degrees in 1 frame = 120 RPM Start
25 degrees in 1 frame = 125 RPM Start
28.5 degrees in 1 frame = 142.5 RPM Start