Many, many years ago, I pulled around a Trail King 70 ton lowboy with air suspension and a detachable single axle (air suspended) booster that projected out about 15 feet from the rear of the trailer (I think it was a General). In those days in New Mexico, that single axle was worth 20,000 pounds and added to the "bridge" length in Colorado. The way the booster attached to the trailer made it rigid horizontally and in line with the trailer. It had to be shimmed so that it wouldn't carry too little or too much. To set the angle correctly, I got a big load on the trailer--to flatten out the camber--and placed shims at the connection of the trailer and booster to angle the top of the booster for the correct weight distribution. It actually worked quite well once I got used to it. Once I got it set to a 100,000 lb. load (the usual) I didn't set again, although I probably should have. When the trailer was empty, I would have to remove the booster altogether or remove a connecting pin to allow it move vertically independent of the trailer. With the camber of the empty trailer, much of the weight of the (rear of the) trailer would be on that single axle. As I recall, there was air adjustment, but much of the adjustment was done with shims. I hope this makes sense.