It's not so much the size of the gold, but rather the unusual texture/shape of many bits that the SDC will pick up that the GPXs struggle on. Going down to a Sadie coil does increase your sensitivity a little, but if you really want to get close to the SDC and get gold more consistently, then I'd be adding a 12x8" Evo, and get your Rx Gain and Stabilizer up as high as you can without losing your sanity haha. Yes you are going to dig some hot rocks and ground signals.
Also if you are not using an enhancer, use Boost Audio, it really helps to lift the fluffy signals.
Also if you are not using an enhancer, use Boost Audio, it really helps to lift the fluffy signals.