Many thanks for that. I really appreciate the translation, it made sense. Well it does explain how the agouti protein is involved in regulation of banding. Interesting that agouti and MSH are in competition for MC1-R, as analogues they'll be from the same gene family, which certainly lends itself to a range of polygenes. I'm assuming given the range of coat colours that Eumelanin and Phaeomelanin are not the only 2 pigments involved, I can see how this could quickly become quite complex.
But it does still leave me with my question (which is effectively the same/similar as Elaine's key question) unanswered. It seems as though something could potentially be upregulating expression of melanostimulin (or more ultimately expression/translation of eumelanin as I guess it could even be due to another pathway) in certain cells, causing some hairs to grow completely black, whereas others remain banded.
It's very intriguing as when I look at my cats 3 of them (2 SBT Bengals and a Blue Tabby Maine Coon) have clear banding that means their pattern is essentially superficial - part their fur at even their darkest point and the lighter undercoat is the same light colour as it is everywhere else, whereas the F2 boy is quite different. His black markings really are full length black hairs, part his fur where he is black, and it's black down to the skin. If I were to shave his fur the stubble would still be spotty! I find it really quite fascinating (small things eh) as its suddenly very obvious that I have not ever seen it before on any cat. (maybe I just haven't lived??
Even without understanding the mechanism, it could be very interesting to start identifying which cats have this feature, and seeing how reproducible it is if lines are strategically bred.