Well, my experience with the 1/2 ton trucks is that if I load 800 to 1000 pounds in the bed, it causes the rear springs to compress about 1 inch at rest and bumps in the road will cause the pads to hit the frame but that extra weight will not cause the front end springs to compress correspondingly. In fact depending on where the weight is, it can cause the front end to lift up due to weight shift and that will cause the steering to seem to float at any speed over about 40 mph...the exception is if I can load all the weight up near the front part of the bed to put it mid-ship. That centralizes the load and minimizes the front end float somewhat. With firewood, dirt, gravel you can't do that, however. The last time I had to haul a complete engine and transmission, the yard loaded it right at the back of the bed and driving home was a real challenge. Same with a front clip for an MG-B. I had to carry one of those to a town 70 miles away and steering was a mess.
Whether the drag link is above or below the line of being level doesn't matter...especially for a front end designed like the AD. If we had a track rod or track bar that was a different length than the drag link then we could have all sorts of different bump steer problems. Those have different pivot points and thus different arcs and all sorts of "arguments" can happen. Our front end works more like a simple 4x4. We just have a solid axle, a tie rod and a drag link so the drag link makes the arc. To minimize bump steer the drag link has to hit the center (parallel). You can see it...very easy to visualize. The higher point on the arc of the circle will have the same effect as the lower point and the higher/lower on that arc the point of intersection is, the more bump steer will occur because just a little movement will pull/push the drag link in an exaggerated manner.
