Great work!
At higher speeds it doesn't matter how much stamina or recovery you have, since you reach the next checkpoint so quickly that you can't possibly use up all of your stamina bar between them. I kept dumping all my points into strong legs and Agility; maybe if the upgrade cost increase each time?
It is a bit jarring to go from moving so fast to suddenly pausing at each checkpoint, unless you're spamming accelerate to quickly skip the