It's usually not the first pass across the field that really strains the tractor as a lot of times you are not getting as much penetration in hard packed soil, but on the second pass your tractor is in loose soil and the offset harrow is now really getting penetration and it lets you know that it's back there. I usually use an Athens 8' or 9' offset I can't remember the width for sure with 24" disc blades, I use it to get my winter rhye pasture ready after summer millet and it will be hard packed from the cows grazing on it all summer, so the ground is to either turn with a plow or bust open with an offset disc and then finished up by running over it with a leveling harrow and a good drag.