What if he made a woman's capsize dependent on their current mood? The larger the happier and the flatter the angrier. Saddness would cause them to sag temporarily, while feeling horny made them lactate profusely.
Not wanting to be left out of the fun, Ken used the margin on the side to turn himself into a 21 year old girl. He gave himself D cups for when he was feeling content (neutral).
When Ken finished writing and closed the book, she already had her new body. Kendra immediately began to feel herself up, only to cause a steady flow of breast milk to start pouring from her nipples. This triggered an infinite feedback loop due to the pleasure she got from lactating was enough to sustain her horniness. So now with endlessly leaking tits, Kendra was excited.
She was so happy that it worked that she soon found herself lugging around the largest tits she had ever seen. And they kept getting bigger too. In a last effort, Kendra managed to collect the book and something to write with before her tits became larger than herself. Kendra fell forwards and landed on her jiggling pile of titflesh. It was like a pair of waterbeds were underneath her body, that she could feel with every inch of.
Sighing, Kendra knew she couldn't keep them like this. So she revised her wording and set a hard upper size limit of +4 letter sizes from the base size. Her breasts began shrinking down until only an enormous pair of H cups remained. At least these were more manageable.
Feeling satisfied, her tits began to deflate, but her milk flow continued on, as strong as ever. She didn't mind that though. In fact, she loved it. Kendra wanted to do more, to both herself and everyone else too.