Thanks Joel. I'm usually in 18-20 on sensitivity or the Nox seems too chatty. For some reason, this site tolerated the higher setting. Truthfully, I was playing around with the bias and sensitivity during this hunt and these were the settings used when the tokens hit. Usually, a brass 21 mm token is a dead on "19" on my Equinox. This one bounced up to a "21" with a bit of a squeal on the audio and I'm thinking I was probably running it a little hotter than I should have been.
I'm not one to tinker too much once I find settings I like. The whole pros and cons of the iron bias on the Nox are still a little confusing to me even though I've read a ton about them.
Like you, I'm thinking "0" bias with a higher recovery setting is probably the best for the type of ground I'm usually in.