The second test was probably invalid. When you take a 1200 pound race car and attach it to a 2000+ pound sled and then crash it into an immovable object, the force generated by that sled and race car combined is much much greater than a race car by itself.

The first crash the chassis performed just the way one would hope it to respond. Most of the energy was absorbed by the front section of the car and the drivers compartment sustained very little damage.

Now I have seen cars flip so violently that the engine goes one way the fuel tank goes the other and the shocks and other parts fly off like shrapnel all around the race track and grand stands.

Honest Dad himself