This is a drag I built out of some scrap steel I had laying around. The sides are just under 5' long and are 8" channel Iron. The blades are from a piece or 10" wide flange I beam that I cut the web out of making 2 flat pieces. The remaining web section (where it flares out at the flange) acts as a reinforcing rib. The front blade I cut teeth into which I ended up reinforcing with some 1/2x1/2 square bar stock (not in picture) to break up the gravel surface. Both blades are set about 1" below the sides to allow it to cut a little. The rear blade is smooth and will hold a good bucket full of loose gravel as I am dragging. The 3 point piece is hinged and attached with chains to allow me to lift it up and also allow it to float with the driveway. I have a grader blade, box blade, and rock rake and none works as well as this little baby. I have over 1500 feet of driveway to maintain and if this thing went down I would order the steel and build another exactly like it the next day. My only complaint is that a certain size rock will stick in the front teeth every once in a while and keep it from cutting well. I don't know if tapering the teeth would help or not. I intended to add a weight box to add weight but it cuts well enough, and carries enough gravel that I think with weight it may not work as well.
Good luck!