Maybe making it optimally sensitive is possible, IF you haven't already done so.
BUT just in case, can you give an example/s of a low conductive target/s...like the ones that you say, can't even be detected on the surface.
Are they made of:
Iron?
Bronze?
Gold?
Other?
I've NEVER had trouble detecting objects made of these and/or many other metals.
Just about ANY metal type(size not included)that I have ever exposed the Explorer to , is detected.
BUT
I do have one gold item part of an earing, that is of a hollow nature BUT is about 1 1/2 inches long that Explorer XS X2 or the SE CAN'T detect and only a high end P.I can just barley detect it at about 1/2 inch. Thats about the only target and some small gold chains that Explorer XS EX2 and SE, that I have have been unable to detect.
Same target fails to register on:My DFX, Tesoro Sand shark, M/L Excalibur.
Not saying that such targets are undesirable to all of us BUT they are usually in the reject area on a default on board pattern.
I am also not saying that such targets do not exist.
Most targets get missed, when close to the coil, if they are excluded from being detected, the user fails to id them, the detector is not set up correctly or the detector and/or it's coil is not functioning or the target mass is just TOO small.
Explorer has it's limits on such small objects.
In this case maybe what is needed, is just that, a detector that you'd use for prospecting or searching for smaller specks of alluvial gold.
Whites MXT or the likes MAYBE or a M/L prospecting detector comes to mind or as you said one with switchable frequencies.
David Di.