For years we maintained a 3 mile gravel road with our home made drag that consisted of 5 6 X 6 8 ft timbers that were faced with 3" x 3/8 blades that we lag bolted on.
The wood frame was notched for strength and used 1/2" bolts.
Tow was 2 chains looped thru 12" tires that acted like shock absorbers.
2 beams were fore/aft with the 3 blades at angle with the first at about 15 deg to the right, the second at about 30deg left and the last 15 deg rt.
First blade would cut bumps and shift material off to the side while filling dips and then the second blade caught material from first and shift it over to left side all while again scalping and filling dips.
The 3rd blade completed the scalping and filling with very little loose material left over.
With this 3 blade design there was very little digging in but rather simple spreading of the loose material that cars had displaced from constant traffic.
Whenever we saw it dig too much we simply increased speed.