This is my first deathless run at 51-100 :)

[Timer Start] When the timer shows 0.04, the edge of Course 51 is not yet red. This means the timer starts at least 0.04 seconds faster.

[Timer Stop] Timing ends when the pop-up after course 100 is visible at the bottom of the screen. At that time, the timer shows 8:53.36.

8:53.36 - 0.04 = 8:53.32, and rounding it, I got 8:53.3