I'm hunting a site that has orangish dirt in S. Tenn. The Vaquero and the X-terra I've hunted it with, using the 8X9 concentric and a 10.5" DD, seem to only be getting an effective depth of about 6 to 7 inches. I'm not averse to adding another machine that can get 10 inches on a Minnie ball in an open field with a little bit of mineralization. Don't know if a large coil would make this worse or more likely to find something period, if it's there. I just want to try and hedge my bet on finding the site I know is there, but haven't located yet.