Re coils, in many cases, a smaller coil may have its advantages over a larger one, especially in trashy ground. Since changing back to a smaller ecliptical coil, I am getting a lot less emi falsing, better performance in iron, and better target separation. Most of my recent finds are coming from the same area, detected over and over again from different angles to seek out masked targets, ones that were "hidden" by falsing and nulling on the larger coil, so I am effectively getting more "depth" simply by being able to hear clearer targets
Sometimes a bigger coil will simply see too much, with multiple targets under the coil at any one time if in junk and iron ridden areas can be very frustrating, although much more suited to the beach where targets are more sparsely spread.