As shown in the post attached above, you can simply use one bungee line, and connect the two cars to one another. The linked drawing shows a pad eye on the front of the crossbar, but you could just run it from one car, the under the front of the crossbar, then behind the dolphin striker post, and then out and up to the other car.

I used to use two bungees, and just run one from each car and tie it off on the dolphin striker. That way, I could get good tension without worrying about moving one car in to pull the other out. I may have been over thinking it at the time...

You mainly just want to keep the bungee away from the rotating mast base. If a bungee gets stuck in there, it will be destroyed.

Mike