With my battery in the trunk, I ran the ground to a nut welded to the frame rail right below it. Then a ground from the rear of the RH cyl head to another nut welded to the front RH framerail down out of site. Batt charges just fine, engine cranks fine (I use the mini-starter), and ground side cable lengths and complexity are minimal i.e. no worrying snaking down to start around headers. This is on the avatar car - street/strip (408 10.5 CR). This was someone else's idea and i did it and it is simple and just works. Hope this helps!
