Yep - this was one of the original threads I used for initial research.
In both this custom kit and also the "GroundingGear 10-wire performance" kit, there are common grounding points:
Battery to headlight grounds (on the strut towers), to the engine, plenum & Throttle body. These are the four the development kit uses, and so far at least all kits have these in common. Whenever possible, it's always best to ground directly to the negative battery terminal, but daisy chaining is good enough since the thick wires resistance is low.
TCU and ECU seem to be other common grounding points. Also transmission. So there's three more wires. Any others? Probably won't do all three of those - trying to keep the kit cost effective.