Need help with 5th wheel install on flatbed

[BWiester]

Here's the situation. I have a 02 with a Bradford Built flatbed. I have a fifth wheel hitch I want to mount to it. I got the hitch for almost nothing so thats why I'm not going with a gooseneck to 5th adapter. Anyway, does anyone have any recommendations on how to mount this. I have everything to the rails, but no underbed mounting hardware. I want to retain the goose neck under the bed, so the rails will need to be both shaved about a 1/4" so the door will still open. Can I mount this to the bed only and sandwitch some plates underneath for strength or do I need to go to the frame. I am a newbie at the 5th wheel thing. I am wiring a shop in trade for a 27' camper and now need a hitch. Please advise.

 

[GSchroeder]

The deck is 1/8" and I would connect to the crossmembers for more strength. I sell Bradford beds and they are stout.

Gordon