I have a hydraulic top link. When used as a flexible top link, I shorten it and add a link from a ship's anchor chain... about 10 inches long. A segment of heavy chain between end of hydraulic top link and attachment point of box blade could be used in place of the ship anchor link, I just used what I had available.
When using the box blade on uneven ground with the fixed top link, I found I had to constantly raise and lower the blade and adjust the angle of attack to keep the blade on the ground and try to level the road out. This is because a compact tractor has a rather short wheel base. When the front wheels rise up on a bump, the box blade is forced into the ground by the fixed top link, causing a dip. When the front wheels drop down, the rear blade rises and drops its load of dirt, causing a bump.
If, however, there is flex in the top link, within reason it will take up slack or gain more slack in the above conditions, maintaining ground contact resulting in fewer passes and smoother road.
In operation, I lower the box blade to the ground, lengthen the hydraulic top link+chain such that there is some slack. I raise the lower two points of the 3ph so that the angle of attack of the actual rear blade is nearly flat, maybe just slightly digging in.
Weight of box blade plus added weights is about 1000 lbs.
I have my own hydraulic trailer and live near limestone rock quarries. Thus, acquire loads of road base for my ranch roads. Try as i might, I can't always evenly spread the new material...sometimes I have one foot bumps to smooth out. This rig helps me.
I am sure that there are many approaches to doing this task...this is how I do it. Suggest you create your own flexible link and give it a try...not terribly expensive.:thumbsup: