Fusing Amps Correctly

[SMZ2]

I need some advice on fusing for pure copper flex-a-prene 1/0 welding cable. I will be doing 2 runs of power and 1 to 2 ground runs. I will have a d3400 up front and 3 d3100s in the cargo space and all running on a 270 amp alt. Then off the rear bank 2 skar 2500.1 and a mb quart 125.4. I am also curious how you would fuse these.

[Josef344]

Are you running from front battery or the alternator?

[SMZ2]

Front battery. What size fuses should I be using? Also how would that diagram look like if I had a bank of 3 batteries?

[SMZ2]

My other concern is what size fuses to use with dual inputs

[SMZ2]

Okay so the skar manual calls for a 250 amp fuse. Some when using dual inputs would each positive run use be a 250 amp fuse? Also since my alt is a 270amp should I run a 300 amp fuse on both positive runs? Finally the mb quart amp has 3x40 amp fuse so what size fuse would be used for that amp?

[SMZ2]

My guesses for fusing please correct me if wrong as I plan to order my fuses and fuse blocks today. 300 amp for each run off the front battery. 125x2 for each 2500 power input since I am doing dual inputs. Then a 125 amp for the mb quart? What if I did dual 1/0 inputs on the mb quart as well though?