UnitySteer - Steering around an sphere

I'm using the following to make objects navigate around a sphere, I've implemented my own crude collision detection but it's not at all ideal for the types of behavior i would like. So i've decided i wanted to try and implement UnitySteer.

 public void Update()
 {        
     transform.position += transform.forward * Time.deltaTime * ForwardSpeed;
        Vector3 surfaceUp = transform.position - Vector3.zero;
        Quaternion surfaceUpRotation = transform.rotation;
        surfaceUpRotation.SetLookRotation(surfaceUp, -transform.forward);
        surfaceUpRotation *= Quaternion.Euler(90,0,0);
        transform.rotation = surfaceUpRotation;
 }

The above is the code i use to have objects navigate around the sphere. How can I use this correctly in UnitySteer and have it avoid terrain correctly?