Removal of Grafts at 6 Months?

Yes, this can be removed but I need to see your before photos and current ones. For 35 years I have not used or had to use rib grafts for primary or revision rhinoplasty. 

Nasal grafts can be removed at anytime after the rhinoplasty surgery. The onlay graft  is the easiest to remove while the spreader grafts are a little more difficult but still can be done. The question is not whether they can be removed but if this is absolutely something you want to do given your investment in the process up to this point. Thus the reason to wait at least 6 months after the initial surgery to let the nose settle and to have the patient gain perspective on the new shape.

It is best to wait a year to go back into a nose after a rhinoplasty. At that time, grafts can be removed if desired.

The decision to do surgery depends on the indications. It is impossible to give you good answer without more information and pictures. What was the reason for the Rib Graft?

To give a useful answer to your question, I would need to know what your original nasal defect was.  I would also need to know why you want the grafts removed.

Typically spreader grafts are used to increase the size of the internal nasal valve (air passage) in the nose and are not particularly visible.  They may widen the dorsum of the nose slightly.

The rib onlay graft may have been used to augment the dorsum of the nose.  If you can feel it or it is bothering you it can be removed.  Keep in mind though, that it was there for a reason.  You may not like the appearance after it is removed.  It is possible to replace the rib graft with a softer graft such as diced cartilage in fascia.

The surgery you are contemplating does not require a specialist in revision but I would first speak with your original surgeon and express your concerns.  Best of luck to you.