My assessment of my own DD6 is that she is at roughly between your DS and DD. I feel the same, just enough on the edge of the spectrum to be undiagnosable. Your assessment of what part of the spectrum you see your DD on is exactly the same as where I would place her.
Interesting you mention the memorization skills. I consider the peak of fact based memorization skills to occur at the edge of the spectrum as well. Those farther into the spectrum or farther away from the spectrum will be weaker at fact based memorization. It is not that people on either side of this point have weaker memorization skills, they just can remember different kinds of information better.
The comprehension skills in my opinion are much more complicated than being a result of what point in the scale a person is at. I have some ideas on this, but I am still struggling to find the pattern in this area.
Socialization is another area, which has some aspects related to the point in the spectrum a person is in. However, there appears to be other factors not related to the spectrum.
From what I have seen, the spectrum also includes both people with poor coordination and some of the best coordination I have ever seen.
