This is just a thought. Could you get some heavy angle iron, and either weld it to the end of the weight tray so you can do the same on the old disc's tray, (see my "CAD" crayon assited doodle below) or if welding isn't an option, bolts? Just not sure how that would work without seeing both discs setting in place as you'd envision them. If one disc follows the other, not sure how you'd handle any sideways forces exerted on the set up during an engaged turning manuver. You'd have to lift it out of the dirt to make any kind of change in direction to avoid bending the rear disc off to one side. Unteresting project, let us know if you proceed and how you approach it. Good luck!!