Hey Togo -
I have a Series IIA. I thought about a similar thing. So I decided to use the liftgate eyelets which are already on the back of the vehicle. I bought two sliding gate latches, which are spring-rods in a housing you can bolt on to wood. I bought a 36in x 24in piece of birch plywood for the table. And I bought two folding shelf brackets. I will do a video of the assembly, because I haven't finished it yet. But the idea is this:
The spring-bolts will be on the underside of the shelf and slide into the liftgate eyelets. This holds the shelf in place and gives vertical support. The folding brackets will be attached to the shelf bottom and fold out against the back of the vehicle preventing the shelf from flopping downwards. When not in use, these fold up nicely and the whole thing is compact.
I'm excited about this project, and will definitely share the results here soon. I thought about attaching a fold down shelf to my rear door, both inside and out, and it occurred to me that his adds extra vertical strain to the door hinges. Why not cook up an arrangement attached the to back tub? It will work well as a nice place to pull up a camp chair and eat, as well as a place to cook using my MSR whitegas campstove, which is small, light, and fairly safe.
I hope this helps!
Mike