I liked that movie a lot.
The plane they created wasn’t really that experimental. It was built from parts of a proven design. The creation was very much lighter. Though it was single engine, it had much less than half the weight and drag of the original craft.
I suspect that the wing mounting points may have been very similar in and outboard of the engines. Using the same mounting design and hardware would have been cheaper simpler in the design and manufacture. Stress, inboard and outboard being quite similar. Even if the holes did not align, they had torches to blow new ones through.
If I were attempting such a thing. I would try and add as much extra control surface deflection as possible. Removing so much dead weight, drag and miscellaneous lift items from the craft would present very unexpected pitch characteristics.
I also thought about creating a land vehicle instead. It would be a wild ride. A very powerful engine. A lot of friction. Terrible terrain. Giving it full throttle up a dune. Then cresting and maybe taking very bad, short flight to the downside. The air seemed a better bet.
A great movie. Really appealed to my tech, DIY self. As well as the well played human problems. They didn’t get too maudlin or stupid with the human interactions in the film. Almost technical there too.