Hello Tim,
When I am shaping a pistol handle I am constantly grabbing it to see how it feels. I can often find high spots that way. I do not know the original you are looking at, but to me it looks like you could make more of a curve on the inside of the handle by removing some material. Not much.
On mine the butt stays rounded and follows the lines coming from the back of the handle. If you chose to make more of a curve on the inside, do not include the very bottom of the handle, by leaving it the bottom will point forward slightly.
I generally remove material around the grip so that the butt is a little wider that the rest of the handle.
Its looking good!
Cory Joe