How do I fake gravity when I disable unity's gravity?

I have gravity disabled for my rigidbody because my game its gravity direction can change and one player can be on a different gravity direction as another. I have a object made out of meshes and I want it to fall apart when I instantiate this object and collapse in the gravity direction of my choice.

I am using the script below but somehow the effect is never the same as when the rigidbody uses unity its gravity.

Its slower and does not entirely break apart when I use my code. Changing my gravity amount does not seem to have any effect and I tried using different force modes. So how do I fake the same gravity or how can i apply different gravity directions as unity only supports one gravity at a time?

 #pragma strict
 
 
 private var currentGravDirection     :Vector3;    
 private var gravityAmount             :float        = 20;
 private var    rRigidbody                :Rigidbody;
 private var usephys                    :boolean = false;
 
 //--------------------------------------------------------------------------------------------------------------------------------
 //   
 //--------------------------------------------------------------------------------------------------------------------------------
 function Awake() :void
 {
     rRigidbody         = rigidbody;
 }
 
 
 
 //--------------------------------------------------------------------------------------------------------------------------------
 //   
 //--------------------------------------------------------------------------------------------------------------------------------
 function FixedUpdate () 
 {
     if(usephys)
     {
         rRigidbody.AddForce(currentGravDirection * gravityAmount, ForceMode.Force);
     }
 }
 
 
 
 //--------------------------------------------------------------------------------------------------------------------------------
 //   
 //--------------------------------------------------------------------------------------------------------------------------------
 function SetGravDirection (gravDir :Vector3) :void
 {
     currentGravDirection = gravDir;
     usephys    = true;
 }