Ballistic Ping Pong Ball vs. Tennis Ball at 450km/h!

Hi ... I liked your video. However, I think there is a small misunderstanding in min 07:20 when you talk about the inconvenience of having a car made out of rubber. You argue that after the collision the spring back velocity will be very high and you relate this to the effect of acceleration in the human body. 
In reality, when you have an elastic material the impact duration is larger and the peak load and therefore the acceleration is smaller. The real problem of using a very elastic material is the protection of the occupants since there will be very higher deformations in the cabin that could harm the people inside.