Lippert components, who makes the frames for Forest River and others, has a memo that you can find on their website that warns against a gooseneck adapter, and will decline any warranty repairs related to the frame on a unit with said adapters. Get a B&W tunover gooseneck ball hitch, which leaves the bed flat and empty, and get the B&W Companion fifth wheel hitch that mounts into the turnover ball hitch. Expensive, but no rails when not towing.