can anyone tell me if the middle shaft section of a pi metal detector can cause depth loss if adjusted close to the coil....im a short person so i adjust bottom fiberglass rod so its short but then it comes nearer the coil and the shaft being made of aluminium surely the coil must detect this aluminium section...i know the detector has auto tune and targets must be in motion to be detected so does the shaft have any effect on 1st amp output ????