How to create a Ragdoll attached to a moving object

I want to create a game where the player is attached to a vehicle from the waist down and his hands and upper body move around like this video.

I have tried the Ragdoll Wizard, and based on that i have user Character joints only on the upper body and connected the torso to the vehicle using a fixed joint. But the result is so jerky that its unusable. I have tried to change the Spring and dampening values but still its pretty jerky.

Any guidance will be appreciated.

 

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