If an airboat ran better with the engine located in the middle of the hull ... they would ( the manufacturers of real ones ) would have come up with something by now )
That is because it isn't pratical. If the prop was more forward in the full size, you would not have any room for passengers or cargo. Each person has their inspiration for their building...mine comes from tweaking what I know about full size boats, then pushing the limits of the physics of the airboat into the little ones....then let the videos do the talking.