I agree that the physics are kinda strange. The bounce when hitting a wall has been toned down a bit for the next update. The reason this happens is because the wheels usually hit the wall before the chassis causing the car to be launched into the air by the suspension. This is quite hard to balance because if I make the chassis extend too far forward it will hit the ground when driving up a ramp for example. I might also experiment with making the barriers higher or a different shape.
I should definitely take some time to go through all the materials in the game. I agree it's too shinny sometimes!
I'm glad you like the game!