I built the basic tool about 10 years ago. It does a great job of leveling and dragging material from high spots to low spots.
I needed something to do the nearly the same with driveway rock, leaving the rock level but to a pre set depth.
I added the mounting plates and the skids which can be set to the desired depth, it works great. A couple of tricks, drive backwards as you dump the rock from the tractor bucket, it makes it easier to drive over for the first couple of passes. Second, remove your top link pin and let the runners follow the road. When your done just un bolt the skids and you're back to your original tool.