The mics in dual systems are usually dynamics, partly so they don't need power the way an electret does and partly because dynamics pair well sonically with piezos. Oh... and all piezos are not created equal - the piezo disks are usually ceramic, while the "hot spots" and other piezos used for guitars are usually polymer, which are smoother sounding and more durable than ceramics.
If your preamp takes two inputs, use that - then you don't need any special cables. Also, the piezos have a very high impedance (usually a few megohm or higher) and you need to keep wires as short as possible to prevent noise and signal loss. That's why premps are usually onboard or at the very least a belt pack.
If you absolutely must have a stereo output, you can either use a Y cable (AKA "insert" cable) or use a stereo cable and make a breakout box (stereo jack in and two mono jacks out).
I should have done this a long time ago - the new paragraph that is.
Tell me about it! Your posts are usually entertaining, but they are difficult to struggle through sometimes - so much so that I think you probably lose some readers/potential advice givers along the way.
