I recently set up our Smart for towing. I have read most if not all the threads here about battery disconnect switch. I think I'm going to add one and put it under the dash where others have. I've read I need somewhere between 18'-24" long cables to run to the switch. However, I have not read what gauge people use. The original cables look pretty small to me? I'm thinking 8AWG? I don't want to go any bigger than necessary.