Move along surface normal of hollowed pipe with cube

Hi all,

I love @Marsupilami 's script here in another thread - https://answers.unity.com/questions/545844/make-player-character-stick-to-the-level-mesh-and.html - it's allowing me to starting moving my player cube around a pipe wall much of the time!

One drawback for me though - I think part of my problem is that I have to allow all sides of the cube to be the normal to the surface. Here's my movement code:

 // Update is called once per frame use fixed update for Unity Fizzix
     void FixedUpdate () {
         //distanceFromPipeCenter.Normalize();
         //add forward force
         rb.AddForce(0, 0, forwardForce * Time.deltaTime);
         
         if (Input.GetKey(KeyCode.RightArrow) /*&& !fauxGravity*/)
         {
             rb.AddForce(sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
         }
         
         if (Input.GetKey(KeyCode.LeftArrow) /*&& !fauxGravity*/)
         {
             rb.AddForce(-sidewaysForce * Time.deltaTime, 0, 0, ForceMode.VelocityChange);
         }
         //if (Input.GetKey(KeyCode.RightArrow) && fauxGravity)
         //{
         //    //Debug.Log("Right pressed");
         //    rb.AddForce(sidewaysForce * pipePull.x*Time.deltaTime, sidewaysForce * pipePull.y * Time.deltaTime, 0, ForceMode.VelocityChange);
         //    Debug.Log(rb.angularVelocity);
         //    float headingDeltaAngle = Input.GetAxis("Horizontal") * Time.deltaTime * sidewaysForce;
         //    Quaternion headingDelta = Quaternion.AngleAxis(headingDeltaAngle, transform.up);
         //    //align with surface normal
         //    transform.rotation = Quaternion.FromToRotation(transform.up, distanceFromPipeCenter) * transform.rotation;
         //    //apply heading rotation
         //    transform.rotation = headingDelta * transform.rotation;
         //}
         //if (Input.GetKey(KeyCode.LeftArrow) && fauxGravity)
         //{
         //    //Debug.Log("Left pressed");
         //    rb.AddForce(-sidewaysForce * pipePull.x * Time.deltaTime, -sidewaysForce * pipePull.y * Time.deltaTime, 0, ForceMode.VelocityChange);
         //    Debug.Log(rb.angularVelocity);
         //    float headingDeltaAngle = Input.GetAxis("Horizontal") * Time.deltaTime * sidewaysForce;
         //    Quaternion headingDelta = Quaternion.AngleAxis(headingDeltaAngle, transform.up);
         //    //align with surface normal
         //    transform.rotation = Quaternion.FromToRotation(transform.up, distanceFromPipeCenter) * transform.rotation;
         //    //apply heading rotation
         //    transform.rotation = headingDelta * transform.rotation;
         //}
         if (fauxGravity)
         {
             float distForward = Mathf.Infinity;
             RaycastHit hitForward;
             
             if (Physics.SphereCast(transform.position, 0.25f, -transform.up + transform.forward, out hitForward, 5))
             {
                 distForward = hitForward.distance;
             }
             float distDown = Mathf.Infinity;
             RaycastHit hitDown;
             if (Physics.SphereCast(transform.position, 0.25f, -transform.up, out hitDown, 5))
             {
                 distDown = hitDown.distance;
             }
             float distBack = Mathf.Infinity;
             RaycastHit hitBack;
             if (Physics.SphereCast(transform.position, 0.25f, -transform.up + -transform.forward, out hitBack, 5))
             {
                 distBack = hitBack.distance;
             }
 
             if (distForward < distDown && distForward < distBack)
             {
                 transform.rotation = Quaternion.Lerp(transform.rotation, Quaternion.LookRotation(Vector3.Cross(transform.right, hitForward.normal), hitForward.normal), Time.deltaTime * 5.0f);
             }
             else if (distDown < distForward && distDown < distBack)
             {
                 transform.rotation = Quaternion.Lerp(transform.rotation, Quaternion.LookRotation(Vector3.Cross(transform.right, hitDown.normal), hitDown.normal), Time.deltaTime * 5.0f);
             }
             else if (distBack < distForward && distBack < distDown)
             {
                 transform.rotation = Quaternion.Lerp(transform.rotation, Quaternion.LookRotation(Vector3.Cross(transform.right, hitBack.normal), hitBack.normal), Time.deltaTime * 5.0f);
             }
 
             GetComponent<Rigidbody>().AddForce(-transform.up * Time.deltaTime * 10);
         }
         if (rb.position.y <-1f)
         {
             FindObjectOfType<GameManagement>().EndGame();
         }
     }

You can see in my extra block of commented code, I've tried using an alternate method to detect when the player has collided with a hollowed pipe object (it starts moving inside the object). I want the cube to be attracted to the wall with a gravitational force relative to the surface of the pipe.

Any ideas?