Would like to be able to pull a modular car with another modular car.

The Vehicle Tow plugin on Lone's website does something like this. Its focus seems to be on towing other types of vehicles such as boats and helis, but an implementation detail by which it accomplishes that is by placing those vehicles on top of a chassis which is being towed by the front modular car, so technically they've already achieved one modular car towing another.

I made an attempt at this some time ago, but could not get the Unity Hinge Joint component to work as I expected. Some interesting results occurred. I had the cars spinning like tops, if you made contact with them you'd die. If you or anyone is interetsed in this code salad I'd be happy to share.