Maybe it's the microphonic, unpotted Custom Buckers that are picking up vibrations of the LP top. That would be in the 16-20khz range that you mentioned.
I've been thinking switching the pcb quick connect system in my SG to my Les Paul because I play the SG more and prefer the traditional method of soldering pickups as to not be limited to Gibson brand pickups. Can this be done?
I'm talking about those Gibson guitars that are stamped with "prototype". Do production models have higher-quality wood than the prototypes, specifically those made during the later Henry J. years? What's the difference?