questions about battery disconnect wiring

Properly protect your whole car and electrical system by using fuses! Start at the + battery terminal and put a 200 amp mega fuse between the positive post and the positive cable. Every wire that splits off the + cable should be fused for the size wire it is with a fuse in a fuse block to protect every circuit.
The + output on the alternater on my car has a 50 amp megafuse between the alternater and the #4 welding cable i use for the alternater output. I am going to fuse both ends of that cable since a short could be generated from either end if the alternater is charging. The #4 is big enough that you can run a one wire alternater and there will be no line loss to affect the internal regulater in the alternater, and everything is happy. If this doesn't make sense right away just look at how a house is fuzed. Main fuses protect from total overload, and each circuit starts with the juice going through a breaker sized for the wire it protects. The fuse should never be rated higher than the wire it protects. And lastly, solder all connections.