TR- as I mentioned above and I believe it to be correct, your hat/skull size doesn't "normally" change in your adult years absent certain factors such as steroid use. The rest of the body changes he's had
The pictures show that "head" change in Bonds, IMO; and, besides reading it, I've also recieved certain info from several people involved in ML baseball who I view as credible sources, that has confirmed this, at least for my humble opinion.
I will admit though that I have a certain bias in that having met Barry Bonds on several occaisons it is not hard for me to think the worst of him.