Hi Charles,
Yes, the flag of the 51st North Carolina Regiment does resemble a RD 4th bunting issue, if fact the first time I saw it in Durham I thought it was a 4th bunting issue too. When I wrote Howard Madaus he set me straight and even gave me several of his line drawings to explain the different issues. That shows you the type of person he was, taking the time to write me, a nobody, and giving me copies of his work. It is a shame that in the book The Flags of Civil War North Carolina also mis-labeled this flag as a 4th bunting issue. Too bad the copy editor didn't catch that error because it is a very fine book. I am not expert either but I do love studying it.
Best regards,
mike