I needed a place to mount a bike rack on my fifthwheel RV but the RV has a fiberglass endcap and no bumper. So, I had a local welder design and fabricate a hitch receiver and attach it to the frame of the RV.
Two metal tubes go across the width of the RV and are welded to the bottom of the frame. A 36" hitch receiver is attached to these two pieces so that it clears the bottom of the endcap and extends far enough so that the bikes clear the back of the endcap. Cost was $250.
After the job was done, I inserted the bike rack and both of us (450 lbs.) jumped up on the bike rack and bounced around. I feel comfortable that it will handle two bicycles.