Airstream and Argosy trailer hitch heights are governed by "two" things.
1. The weight that you have added (payload).
2. The condition of the axles.
Two like year and model trailers would probably not have the same ball height, because of those two factors.
The "ONLY" accurate way to determine the ball height of any trailer, is to load it for travel, level the trailer, and then measure from inside the coupler to the ground. For heavy duty suspension tow vehicles add about 1/4 to 1/2 inch to that dimension. For a softer suspension tow vehicle, add 1/2 to 1 inch.
Level the tow vehicle, then set the ball height.
Keep in mind, that the purpose of a load equalizing hitch, is to keep the trailer level, with respect to itself, and, to keep the tow vehicle level with respect to itself.
Additionally, the load equalizing hitch will then redistribute not only the tongue weight, BUT, also the trunk weight.
At the same time, the torsion bars, depending on brand, should bend 1/2 to 1 1/2 inches. That further signifies transfer of weight.
When the bars have little to no bend in them when hooked up, they are not transfering much weight. That then keeps entirely too much weight on the rear axle of the tow vehicle and not enough on the front tow vehicle axle. That results in very poor steering stability, and makes the entire rig highly susceptible to dangerous sway conditions.