Tuning experimentation

I've been tinkering with the tuning menu for a while now, and I noticed that you could go lower than A0 and higher than C8 which are the typical range of the piano. As you all may know, the MIDI note range is 0 to 127 (meaning 128 keys). Currently I am trying to find a way to somehow access the lower notes using the "string tension" or "full rebuild" mode in the tuning menu. Is there a way to access all 128 notes of the MIDI note range (with the lower notes audible of course) meaning being able to hit the lowest C (C-1) and the highest G (G9) both of which are currently accessible when down-tuning the keys in the tuning menu.