Smallfoot gave you good advice.
I use the Pro myself, and would say this. I broke an ear on my large coil, bought the 5 X 8, and haven’t noticed much difference in depth, but maybe a little better in separation. The trick with the large coil, is when you hear a target sound, use a very tight wiggle to pinpoint it. That way, you won’t hear other objects lying close to your target. As you wiggle your way back across the target, your coil could start picking up on a new object, so go 90 degrees, and pinpoint it again. Use the Pro mode, always. Run your iron disc at 30 - 35. I dig everything, because I find neat buttons, and rings, in the pultab range. You might try going over a area in coin mode first. That pretty much blanks out nails, bottle caps, and small iron bits. Be sure to overlap your swings. Good luck and let us know what you find.