In rereading your original post I realized I misread it and you're looking to level it not so much grade loose material which is what mine does, but I'll post it anyways just for ideas.
After digging it out, it's only about 4 ft long, but you can see turned the up rear end of the skid (the front looks the same) and the slotted vertical depth adjuster which was right by the blade. Above that you can see the bolts that fastened the sideplates to the bracket I put on the backblade itself. Hidden behind that leaf is a bolt through the front of the sideplate that acted as a pivot point that allowed the skid to stay flat on the ground and adjust and maintain the blade at the desired height and lay a consistent depth of loose material.
The best way to visualize leveling is to think of a road grader. The blade is in the middle of a long wheelbase tractor that bridges over bumps and depressions.. The front wheels go over a bump then the blade comes along on the same plane and cuts the bump off and if there's a hollow after, drops the cut material in the hollow.
You had the right idea with your skids (walking beams) and they could be modified with wheels on each corner and adjusters for the height of you blade, but would be complicated.
A simpler method and one of the best homebuilt levelers/drag I ever saw was built with heavy angle iron very similar to the one in this video. except the front angle was lower with teeth to act as a scarifier. We had one on our (public) sand road in Florida made from railroad ties. It was parked in a wide spot at the end of the road and when the road got to rough, one of the ranchers would drag it up and down a few times and park it again.
Road Driveway Drag 2 - YouTube
You can search road drag grader and you'll see a bunch of idea's. -------- somehow I got 2 pictures.
Here's a 3 wheeled walking beam grader to do your whole driveway at once.
http://www.tgschmeiser.com/pdfs/Ope...TACH][ATTACH=CONFIG]523274._xfImport[/ATTACH]