Leo,
That is the way I would have installed it in my truck, but the previous owner already had the ball mounted permanently in the bed /w3tcompact/icons/sad.gif.
My old gooseneck trailer had a rather unique design to it. It was the opposite of a semi,,, meaning the kingpin was in my truck bed, and the 5th wheel was on the neck of the trailer. What I liked about this design was when, not using the trailer, you could step on the kingpin and it would go down in the truck bed, making the bed look normal.
The drawback to this design is you would have to be very careful when hooking up, because you would have to "slide" it on to the kingpin. I like "dropping" a gooseneck onto a ball better!!!
RedDog