For the guys who are running Flatbed bodies. I'm planning to drop in a flatbed with a gooseneck trough. Either a CM or Herrin or suggestions? What I can't find out is how their goosenecks receivers are built into them. As from what I can seek in the video or pictures, its just a type of welded "box" receiver that the ball drops into. I'm assuming these are not tied into the trucks frame? Or during installation, they add the receiver to tie into the truck's frame? So does the whole flatbed support the load of the gooseneck rating? I'm a little confused how it ties into the truck. Set me straight.