Julien, what coils are you using at these sites? Is the main nulling problem mostly from the iron targets or the ground? There's not much you can do about the iron nulls but if it's really bad ground that's causing the nulling auto sens. might work better. I've tested this over and over and you will get better depth and target response in auto than you will trying to break through a ground null in manual. Trying to pick up good targets in a constant null from ground and iron at the same time is hard. The first thing I do at these type of sites is turn iron mask off as my first approach to handle the mineralization. There are some really bad sites where I have had to use iron mask off and auto sens. but most of the time turning iron mask off is sufficient. I don't worry about not finding good targets in iron when turning iron mask off. In this case the BBS Technology still enables the detector to separate ferrous and non ferrous in most situations and with the narrow field of detection with the DD coils I seem to pull more good targets with iron mask off at these sites.