Hey BillNope. There's no side-to-side motion. I used chains on my B7800 rear
blade and it works extremely well. The only motion is up and down
as the blade following the contours of the driveway. The weight of the blade
scrapes the drive very well and the independent up and down motion insures that
the whole blade is in contact with the driveway.
The 3pt hitch check chains (turnbuckles) keep the blade from swinging side to side.
Bill
You're correct Usta, 3ph arms will float up at will as there is no downforce. I think what the poster is referencing is that the chains allow the two sides to float independently whereas rigid arms would cause them to float up in unison.