PSA to anyone out there installing a Flexcore - make sure your battery voltage does NOT touch ground, or even come close to it. Many older preamps connect the negative battery voltage to ground, but the Flexcore keeps them separate, and you will fry your preamp if you connect them. Even touching the voltage connector with needle-nose pliers that are too close to your copper shielding can be enough.
So wrap your batteries in electrical tape if your cavity is shielded, and be very careful if you hook up a battery box or any other alternate power source.
On the positive side, Mike Pope is an awesome guy!
Best preamp on the market IMHO.