Revising RNY to DS is not the same as doing a virgin DS. It's a much more complex and challenging surgery, as the entire RNY has to be taken apart, the stomach has to be put back together, and THEN the DS sleeve is created. So I don't mean to say anything against Dr. Barker when I say that he may not have experience with this surgery despite his other bariatric surgery experience.
Dr. Stewart in Denton, TX would be the closest to you that has done this surgery. Other excellent surgeons have already been named. I would recommend you consult with Dr. Stewart. At the very, very least, ask Dr. Barker specifically what experience he has with RNY to DS revisions and go from there.