Your piezo strip is obviously intended to plug into a preamp. So I'd either think about fitting an acoustic guitar preamp for the piezo, or else take the piezo output to its own jack (or you could fit a selector switch for piezo or magnetic output). There will only be two wires in the piezo lead, the ground/braid and the signal wire.
Without a pre-amp, the piezo will need to be fed into a pre-amp with an input impedance of 10Meg or more, in order to get a flat frequency response. So that means either a dedicated acoustic amp that has a 10Meg input, or an external acoustic pre-amp pedal.
So it may be best to fit a cheap pre-amp somewhere into the body. Hopefully with an adjustable volume output so that you can at least pre-set it so that you can set it to match the magnetic pickup output, which would then allow you to set a blend of magnetic and piezo sounds, for whatever you think sounds the best mix. So you could then run with a blend pot, master volume and tone (though tone is always optional).
thanks Simon, I may be limited by the body thickness, so I’ll need to see what is about.
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