One important point about ground cable: it should be exactly the same size as the power cable that's going in to the amp. If you've got 4-gauge power cable going in, you should have 4-gauge ground cable going out. 8-gauge going in? 8-gauge going out. No exceptions.
Now, I'm having 4gauge into power distributer to 8 gauge to the amp.
I was planning on doing 8 guage out of amp to ground distributer to 4 gauge to actual ground. Does this work?