The tuning curve is applied on the final fine tuning. The overpull (maximum) percentages are based on general response from pianos that have been tested by the folks who program the machine. The machine then determines the specific amounts of overpull apllied based on the past notes you havee been tuning. Sometimes I reduce the maximum percentage amounts (default)they program in the machine. If the piano has a weak structure, is very old, has rusty strings ect...I will reduce the overpull percentage. I will often do this on the area of the wound strings also to avoid breakage, especially if I have seen some of them changed out in the past.
As one gets familiar with the results of overpulls on different types of pianos, you begin to make small adjustments on the maximum settings to get better results. Because these are pitch raises, I pick a template of a past piano that resembles the one I'm working on in size. The tuning curve of that template will be close enough for the pitch raise. Before the final tuning, I will properly sample the piano and choose the stretch I want in the program.
As an additional assurance that the correct stretch is chosen, an aural tuner can set a series of (octave)sample notes by ear, sample them, and compare to the cents readings of the fine tuning template. I'm not sure if Verituner can do this but RCT can.
George Brown College /85