This is a real good read and sums up my theories in a nutshell and reads easy
http://wingspanartsintl.com/pdf/X_Factor_PartI.pdf
and why I am stressing a direct tail female meaning on the very bottom of the 4th quarter the x trail. The horses mentioned above were direct tail female meaning the chances of the mitochondrial DNA being passed forward should be greater when doubled from the 2nd quarter (stallions dam).