I don't think just a bypass resistor is going to be enough to keep the piezo mic from sounding tinny, so I hunted down a schematic for a better circuit and plugged that in. The person who made it meant it for a guitar pickup at 9V, but I think it should work for a throat mike at 3.3V as well. I don't think I'll actually know for sure how well it works until I have the board in hand, with components.
I think this (once I've double-checked the routing) probably will be the version of the board that I have printed (sans components) to check header placement. I'm particularly uncertain about the SPI header (at the right-hand end), though the standard Arduino headers may be a tiny bit off as well.