How to boxcast where a dynamic rigidbody2D's box collider will be in the next frame?

Essentially I'm trying to boxcast (Physics2D.BoxCastAll, in FixedUpdate) a dynamic rigidbody2D's box collider one frame ahead of where the rigidbody2D will end up (to see what it will collide with in the next frame, if the boxcast hits something). I'm using the velocity, scaled down by * Time.fixedDeltaTime, but currently the boxcast is much farther out than I would expect, a distance/magnitude too big.

Here's a crude drawing of what seems to be happening.

     private Rigidbody2D rb2d;
     private BoxCollider2D bc;
     private RaycastHit2D[] cast;
 
     // Use this for initialization
     void Start () {
         rb2d = GetComponent<Rigidbody2D>();
         bc = GetComponent<BoxCollider2D>();
         cast = new RaycastHit2D[5];
     }
     
     // Update is called once per frame
     void FixedUpdate () {
         
         if (!rb2d.isKinematic)
         {
             cast = Physics2D.BoxCastAll(rb2d.position, bc.size, rb2d.rotation, rb2d.velocity * Time.fixedDeltaTime);
 
             //Debug.Log(rb2d.position + ", " + (rb2d.position + (rb2d.velocity * Time.fixedDeltaTime)));
             //Debug.DrawRay(rb2d.position, Vector2.up, Color.white); //rb2d.position + (rb2d.velocity * Time.fixedDeltaTime)
 
             //Debug.DrawRay(rb2d.position + (rb2d.velocity * Time.fixedDeltaTime), rb2d.velocity * Time.fixedDeltaTime, Color.magenta);
 
             if (cast.Length > 0)
             {
                 foreach (RaycastHit2D tran in cast)
                 {
                     Debug.Log(tran.collider.gameObject);
                 }
             }
             
         }
     }

Thanks for any help.