The thing about the Garage Shooter is that he's got this slight fatso quality to him. And we see that on Bookhout. Look at his neck, the way it bulges in back.
I suspect they built up his hat, turning it into a top hat, on the right just to hide how short he was. Doesn't it look like a layered cake? Here's a frame that doesn't look doctored. It shows you how the hat really was.
That's your Garage Shooter right there. I guarantee it. Bookhout didn't change much over the years.