I'm not sure the scientific value of towing another car, but I very much like "see what happens" part.

The big lesson that I've taken away from this is that the forces required to mess up the line, much less the buckle, seem to be on a whole other level than we exert hammocking.

I'm leaning toward applying some measured weight to it next, but I don't have access to much. Between my friend and I, we might have 500 lbs of plates, but I'm sure that won't do anything.