well Wayne, I am not sure when they quit growing, but Wylie did slow down at about 10-12 months. He is still growing a little bit, but not too much. I have heard that MC's will continue to 'fill-out' until about 3 years old.
It seems to me also that (sometimes) the bigger the cat, the more gentle they often are. At least that has been my experience.
I hope you are still taking picks of all your kittys!