Honestly the incest and age of the girls hit a niche I have for the taboo, and I find them strangely erotic. Obviously it stays 100% fantasy though. What trumps my interest in the taboo however, like you, is the description and progression of their growth. I love how they not only grow enormous, but they are incredibly excited by the idea of growing even bigger.

It is definitely conflicting, but it's just so hot how happy and big and sexual they all are! Any others besides those 3?

Daddy's Not So Little Girl and then Daddys Big Thingie - both can be found on Chili Parmers Story Archive on the BE Archive. All of these I believe are written by the same guy who wrote the original Fertile Valley. Same writing style, same concepts, same fetishes. Not very good at providing real endings for the stories. They're either left unfinished or all of sudden the ending is rushed. Still good smut though.

This guy has good stories including a google drive called "Forbidden Stories!" (warning bursting)
https://muchbirth.deviantart.com/