Great work so far, Great fabrication skills
From the looks of it your mounts are rather solid, are you expecting a lot of vibration through the car? I've been in cars with rather stiff poly mounts and theres a fair bit of shaking.
IMO the PC680 is fine for a daily driver, I've had no problems and I've been using it for almost a year. Although the only thing it ever has power is the headlights at night and very rarely a radio.
Just make sure you diconnect the negative if you will be leaving the car for over a week.