''I cited the marriage of Ynaa/Yuya and Thuya as a ready example of the kind of intermarriage which produced this result.''

Well,actually yuyaa was not a native Egyptain I have tried to point out to people.

Thuya might have been a native egyptain,but see this is not known either.

''And if Negro is not a term equivalent to Nubian then maybe those Nubian dynasties weren't Black ''

Okay,here is where I disagree with you,because it seems as if you are trying to rehash the old true negro myth which has been thrown by the wayside by physical anthropologist.
People can have aquline noses and lighter skin and still be considered negriod without caucasoiud admixture. Nubians for the most part still look black to me,and if you would ever take a trip to dongola in modern day sudan they have kinky hair and everything.

I will direct to a peer reviwed shomarka keita on the issue of the true negriod myth

Bioanthropologist Shomarka Keita believes that people with "Caucasoid" skulls such as those of Iman or Haile Selassie should be considered just as African, biologically speaking, as people who live in the Congo. He criticizes the tendency of some experts to restrict the definition of "African" only to those Africans who exhibit the most exaggerated "negroid" features (such as extreme prognathism). Keita writes: "In general, this restricted view presents all tropical Africans with narrower noses and faces as being related to or descended from external, ultimately non-African peoples. However, narrow-faced, narrow-nosed populations have long been resident in Saharo-tropical Africa... and their origin need not be sought elsewhere. These traits are also indigenous. The variability in tropical Africa is expectedly naturally high. Given their longstanding presence, narrow noses and faces cannot be deemed `non-African.'" (S.O.Y. Keita, "Studies and Comments on Ancient Egyptian Biological Relationships," History in Africa 20 (1993), page 134)