I had a extendable bumper for my 75 F-350. It was basically the step bumper mounted to a pair of 2" square tubing. The tubing was mounted using pass through hitch mounts, welded to 3/8" plate steel, attached to the frame where one would normally mount a hitch.
So in the forward position, the step mount was near the tailgate, and everything looked normal from outside the truck. The 2" tubing extended about 24" in front of it's mounting hardware.
When you remove the hitch pins from each side, and pull out the bumper about 18", you put the pins back, and where ready to install the camper. In your case, if you can make it extend out another 12" or 24", you will have space for that patio.
Or you might want to make something that folds up while driving, and drops down about 9" to 12" below the camper step in hieght while parked. This will make it much easier to get into the camper while parked, and would be out of the way if you ever drove down a dirt road.
Good luck on the project!
Fred.
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