[Calum]

Originally Posted by Flat Black VW

Not as effectively as what?

Grounding to the body of a spot welded unibody car is less effective then using a properly sized wire.

Originally Posted by Flat Black VW

Not all alternators have a bolt for the battery to ground to and when they do the battery still has multiple grounding locations in your engine bay.

All alternators are grounded through their body. Simply removing one mounting nut or bolt, slipping a ring terminal under it and putting it back together gives you an alternator ground.

I'm really not sure why multiple grounding points in the engine bay matters. Having a ground path that's as short as possible and has as few connections as possible does matter though.

Originally Posted by Flat Black VW

Not to mention the fact that the shorter your ground cable is the better,

Clearly we agree on this point.

Originally Posted by Flat Black VW

meaning having a cable running from the back to the front is not as good as simply grounding in the back.

And just as clearly we disagree on this point. The body of the car can act as a path to ground but it is not the power supplies ground. Also this method increases the number of connections.

Originally Posted by Flat Black VW

Also when grounding in the trunk im not just drilling a hole though the floor pan and grounding it there, im running it through existing bolts, I like using seatbelt bolts at the bottom of the seats, some of my installers like using other points, but its not just to sheetmetal.

We also agree on this. If you do choice to ground in the trunk a seat belt bolt or strut bolt is often the best option. Though some have argued that the seat belt bolt could cause a safety issue.

Originally Posted by Flat Black VW

Another point, if you are running the battery positive to the alternator and the alternator doesnt have 2 separate positive outputs it generally a good idea to use a battery isolator to keep the two batteries separate.

I agree on the battery isolator, but I'm confused as to how we circled back to two batteries. When I wrote about running a wire from the battery positive to the alternator B+ I was talking about doing this with the main battery of the car, not adding a second battery.