[dsraven]

remember to size the cable for the max load it will carry. neg cable needs to be the same gauge as pos. the smallest cable in the circuit will become the weakest link in the electrical chain. fuse each circuit accordingly to the max load it will carry. use relays in circuits that will carry more load than a regular switch should be expected to handle plus the relay idea keeps the wire gauge size smaller in the dash area because those wires become signal wires instead of circuit load carrying wires. the under dash harness becomes more manageable because it is more flexible.
make sense?
look under the dash on newer cars, the wiring is smaller gauge because there are more relays running in newer cars. the relay is under the hood close to the battery so the large wire circuits are shorter, for less voltage drop issues, plus the harness in the cab is smaller gauge wiring so easier to work with and less chance of something rubbing through on an edge and melting an entire harness or catching the car on fire, plus the bulkhead connector is smaller gauge wiring so more easily sealed and smaller overall.