"Tumbling" Projectile (e.g., grenades)

Last night I implemented a simple mechanism for throwing a grenade. However, I can't seem to get the grenade to tumble in flight. It arcs beautifully, maintaining the same orientation until it hits something.

Here is the scripting code I use to create and "throw" the grenade:

%spread = 0.05;

   %throwForce = %owner.throwForce;
   if (!%throwForce)
      %throwForce = 7.5;

   // Get the throw vector. This is the dead straight aiming point of the gun
   %eye = %owner.getEyeVector();
   %vector = vectorScale(%eye, %throwForce);

  // Add a vertical component to give the item a better arc
   %dot = vectorDot("0 0 1",%eye);
   if (%dot < 0)
      %dot = -%dot;
   %vector = vectorAdd(%vector,vectorScale("0 0 8",1 - %dot));

   // Get our players velocity. We must ensure that the players velocity is added
   // onto the projectile
   %vector = vectorAdd(%vector,%owner.getVelocity());

   // Determine our random x, y and z points in our spread circle and create
   // a spread matrix.
   %x = (getRandom() - 0.5) * 2 * 3.1415926 * %spread;
   %y = (getRandom() - 0.5) * 2 * 3.1415926 * %spread;
   %z = (getRandom() - 0.5) * 2 * 3.1415926 * %spread;
   %mat = MatrixCreateFromEuler(%x @ " " @ %y @ " " @ %z);

   // Alter our projectile vector with our spread matrix
   %vector = MatrixMulVector(%mat, %vector);

   // Create the projectile object
   %grenade = new Projectile() {
      dataBlock        = GrenadeProjectile;
      rotation =  "2 2 " @ (getRandom() * 360);
      initialVelocity  = %vector;
      initialPosition  = getBoxCenter(%owner.getWorldBox());
      sourceObject     = %owner;
      sourceSlot       = $WeaponSlot;
      client           = %owner.client;
   };

   MissionCleanup.add(%grenade);

I thought that the "rotation" would do the trick, but it doesn't seem to do anything at all.

Any pointers?

Thanks.

-David
Samu Games