you have the physics backward and need to apply some model theory.
Simply put, mass is the cube of dimensions, while frontal area is the square. So larger/heavier riders gain advantage as their mass increases faster than their frontal area.
Simple rule ----- the
terminal velocity increases with size, which is why squirrels don't get hurt falling out of trees and humans do.
The concept is captued nicely by
Haldane in his essay
On Being the Right Size You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.