Hello Folks
When I bought my 2 yr.old 2013 Scamp 19 deluxe. I took my 07 Silverado (69 1/2 ft box) and goose neck attachment to a hitch shop said that I wanted to place the ball aft of the rear axle other wise the rear bumper would be too close to the bottle rack. They did it and it worked good for 2 yrs. I just bought a 2016 Silverado 69 1/2ft box in Florida and again I brought my attachments to a hitch shop and they would not place the attachment aft of the rear axle. I went to three other places and was told the same thing---the attachment is meant to be placed over the rear axle and they would not deviate from that. So I set the attachment over the rear axle and brought the truck in at a an angle over the ball and I think the truck and trailer will not come in contact in a turning situation (only by inches). This could work. I'm thinking there may have been a shorter box option that I was not aware of that may have worked better with this trailer.
One shop In Jacksonville offered a sliding attachment. When traveling down the road the ball is locked over the axle. When doing sharp turns, you pull a lever to slide the trailer to the rear allowing you extra distance needed.
Any constructive comments or suggestions appreciated
Scamp's answer to the question anything shorter than 60" from the ball center to the end of the truck bumper is good. Others and myself mounted the hitch slightly behind the axle so the tailgate could be be opened while hooked up. (Old style hitch). With the newer standard 5 th wheel hitch if you use a truck specific hitch the attaching hwd. for the bed rails have to match up with holes in the frame so there is not an optional mounting position for the bed rails. They also may have liability issues. Sliders are expensive and heavy. I would look at modifying your existing removable portion of your hitch. (Move ball to rear.)
Eddie