Just to clarify about the MFD Weight Chek, i am talking about right near the cut-off point for a small target. A difference of 50 ohms on the control dial can start to filter out the target. A couple things happen, the response starts to get weaker and the rods take longer to open back up so usually this means you go past the line. So it's not really more accurate once you get to that point. This is where the fine tuning can really help-tune just enough before the response slows. Now this is for the unit i have. It's not like either of the ones on Carl's pan page and it's not like the ones Dell was selling a couple years ago. I just scabbed this one together with Gorilla tape.
Probably build a new one someday.