grounding to rear seatbelt bolt

[Bakerman]

to the OP, just use the strut tower bolt. Sand the paint off to bare metal and put a washer on top of the terminal before you tighten the bolt back down so you don't mess up the terminal. Or better yet get under your car and see if there is a spot that you could drill through and put a nut and bolt through, like your spare tire well.

In the argument of which is better; ground or direct battery run.

Take into consideration that when you ground to your car's body the power has to flow through all of the metal back into the battery, along with the power of all of the other things that are grounded in the car. In essence, if you do a direct ground to the battery, that direct line WILL have more stable voltage than a simple ground because it is just the amp on that line being grounded, not 127 other things in the car.

Edit: typo

I wasn't aware that it worked like this. I always thought that the vehicle was a ground itself. Oh well, guess when things are explained right, you learn new things every day. But all in all, i believe the strut tower, spare tire well, or the frame is sufficient enough ground for his setup.