Fun gimmick, was fun trying to incorporate tricks and stuff into my jumps too.
Not sure how the scoring works, you gave a run down but it felt a bit weird when I used the car that travels at like lightspeed and covers the entire canvas with one splash and got only slightly more than the soup can where I barely touched the canvas.
I'm not sure if it was just me but, after unlocking the last car I saw no way to actually use it?