Can you use a seated dime instead? More realistic with a square nail. lol. Seriously, though I think it might make a difference if it were buried (say about 4 inches) because you can better assure that the coil is a fixed distance from the targets if you are going to run a multi-detector test. As far as Deus settings are concerned:
GB: Manual, within +/-3 of actual GB reading or use tracking.
Ground Notch: Fully cut in (Expert setting under Ground Balance - press the "-" sign until the entire bar is black)
Disc = either no disc (-6.4 for ver 4) or disc=10 pretty much covers the gamut. I personally like to hear the iron, others like to disc it out. Either way works and should not affect detectability.
Expert:Tones = Full (again a personal choice that does not really affect detectability). Obviates need to set up tone breaks and iron volume setting.
Sensitivity = 90 is a good Middle of the road option.
Expert: Tx Power = 2
Frequency = 8 or 12 khz (at 4 inches shouldn't matter what frequency you use, these are the most common choices. Use the one that is less chatty wherever you are doing the test, you can even use 18 khz, if necessary)
Reactivity = 2.5 or 3 > this is the most crucial setting, the one that most affects the ability of the Deus to separate high conductors from iron. Higher settings will enable faster recovery at the expense of less target signal duration. It would be interesting to see the lowest reactivity setting that would allow the target to still be captured.
Expert: Silencer = -1 (off) or 0, though it would be interesting to see how higher silencer settings would affect detectability. Higher settings might allow the nail signal to break up more, but depth is impacted
Audio Response: As desired. I typically just use 4 which gives a little lowering of signal response volume for deeper targets but they can still easily be heard.
Notch: None