Per this thread (http://www.rx8club.com/showthread.php?s=&threadid=14728)
I built and installed a grounding kit, but I would change two dimensions. Terminal B1 and A3 should both have an 8mm hole rather than 6mm per the others. I would then attach B1 to the accessory terminal on the battery negative cable, rather than use the clamp bolt. A3 I have attached to a grounding bolt on the aluminum portion of the intake manifold which appears to be the same as the Japanese instructions.

Yes, good plan. When we put the Mazda one on Canzoomers car we filed out the hole on the battery -ve terminal to fit on the stud. The Mazda kit fit on the lower intake manifold grounding bolt without modification.