how to change sphere/capsule collider, it sizes and the center

I made an enemy that can transform into ball and robot. The enemy start as a ball with sphere collider and when I get closer it transform into robot. The problem is when it transform into robot, it's need to change the collider onto capsule collider because it's legs don't have a collision so they go through the floor. I sucsseed to switch between the colliders tipes but when I tried to change the size and centers - it don't do that and don't change the collider tipe anymore. How do I change the collider tipe, size and centers?

This is what I did so far:

 function Attack ()
  {
      if (canAttack)
      {
          rigidbody.AddForce(transform.up * 40);
          animation.Play("TransformRobot");
          yield WaitForSeconds (0.3);
          Destroy(collider);
          var capsuleCollider = GetComponent ("CapsuleCollider") as CapsuleCollider;
          capsuleCollider.height = 5;
          capsuleCollider.radius = 2;
          capsuleCollider.center.y = -0.5;
          canAttack = false;
      }
  }
  
  function FindWaypoints ()
  {
      if (!canAttack)
      {
          rigidbody.AddForce(transform.up * 40);
          animation.Play("TransformBall");
          yield WaitForSeconds (0.3);
          Destroy(collider);
          var sphereCollider = GetComponent ("SphereCollider") as SphereCollider;
          sphereCollider.radius = 2;
          canAttack = true;
          rigidbody.AddForce(transform.forward * 100);
      }
  }