I had a bike rack (Saris Bat Rack) years back. It worked ok but never really trusted it. Nothing but rubber straps to secure the bike. Then the sloping tubes came out and never have attached one to the rack. I just use the extending bar across my bed.
Some people have used a flat piece of wood, then attached fork mounts to the wood. Lay it in the back of the truck. Pretty secure too. I have done it just as an experiment. Worked well.
But I carry mine like this on a bar.
Unless you insist on a hitch mount, this might be an idea for you.