The seat of a second stage lifts off the orifice by little more than a millimetre. A lever set below its optimum height wastes the most productive part of its travel and may never open the valve fully.
Enter the length of the lever feet and how far the lever turns to see the throw at every step. Add the orifice diameter to see the throw it takes to open it fully; the calculator warns when the lever falls short or leaves too little margin.