I may be wrong, but 4.5 has for years been pretty much the basic size grip for an adult.
I use a 4 5/8 grip; I'm 6'2", 185 lbs., usual size. I have a 4 1/2 grip on one frame, which makes it a little nicer for serving. But the larger grip makes, for me, more stable and firm groundstrokes from the back of the court.
To Praise, To Bless, To Preach--the Dominican Order