yeah defrost is a must w/ the humidity in the mid west. Arizona/Cali you dont have that prob. much i guess..
Welded in my emergency disconnect bracket and mounted the switch up by the dash. Then i ran the ground wire under the dash and over to the battery box through an exhisting grommet. I also decided to respray my dash board after cutting the notch for the battery wires. I didnt like the center painted w/ the carbon fiber look so i sprayed the entire dash w/ the bed liner spray, clean and simple.
I have the same battery disconnect as you. Do you have the wiring instructions for it?