Pre stretching cable/ Prop differences
I think someone was putting you on. A pull pull cable will not lengthen or shorten merely by moving an elevator. the only thing that alters the length is summer heat and winter cold. When you set up your pull pull you must put an adjustable clevis at one end of each cable and check and adjust the tension at the start of every flight day. Plane props work the same as ship props, only one turns in the air the other turns in water and the pitch determins how far forward you move at each revolution.