I have a 4500 GPX and wonder if the soil on Cole's mountain, etc, is too hot for a mono coil to work well? If you use a mono coil on any GPX, which mono coil do you prefer? I'm using the Platypus right now, and it's a DD (waterproof). It works well, but the greater the depth, the more likely I can find deep targets (good or bad) that other detectors cannot reach. Thanks.