Restoration of cheap 12-string guitar, with new homemade pickup

I bought a cheap Japanese Yamaha-copy 12-string guitar at a second hand store for $50. It had an over-bellied top, a bushing missing from one of the tuners, old strings and a misaligned nut. I hung it in the garage for months, planning to torture it as a repair experiment.

Then, as I researched repair methods for over-bellied tops, I discovered the JLD Bridge Doctor, a simple, mostly wood device easily installed inside the guitar that flattens the top and also acts as a soundpost, improving the sound as well as the playability. $22.50 plus $8.50 shipping later, I proved its value.
The metal piece sticking out to the right is the allen wrench used to make final adjustment when installing. It is removed after the bridge doc is in place.

I added a strap pin to the heel so I could hang a strap there ($1), reset the nut and replaced the missing bushing with a used one the music store gave me for free. I had to replace the bridge pins because 3 of them broke when I was removing them to replace the strings, and I wanted them all to match ($5). Finally a new set of strings for a 12-string at $16 and it was ready to go. Total investment so far, not counting my valuable time of course, roughly $113.00, and a very playable, nice sounding jingle jangle morning to ya. I was ready to call it quits and move on to bigger and better projects, but then...
A friend had an oud with a "home-made" pickup system in it for amplification. It didn't seem to be working for him, so he took it out and gave it to me...his wife asked me to throw it away for him....there's a story in there, I'm sure, but that's a different note. It was a simple set up: a 1/4" audio jack soldered to a volume knob and then to two piezo disc elements. These are cheap ubiquitous electronic components that are found in all kinds of devices: telephones, doorbells, buzzers, speakers. I did some research and came up with a plan to 'electrify' the 12-string with a cheap do-it-myself pickup patterned after my friends discarded setup. If it worked, I figured, I'd have enlarged my skill set and I’d have a means of amplifying any acoustic instrument. If it didn't, no great loss. 2 piezo elements, a mini volume control, a 1/4" audio jack and 12" of shielded cable at Radio Shack ran me $10.72 including tax. Soldered it all together, following the pattern on the discarded system my friend left with me,
drilled two holes in the side of the guitar and mounted the jack and volume control,