I will be working out of my Montana this winter but I hope not to the extremes that you'll be in! I already have added extra insulation to the belly and have ALL fresh water line heat taped and wrapped with foam, a most in cold weather. Don't think I'll have to go with skirting but it will save on heating cost!
I'm looking at heating pads for the tanks and is something you should look at.
http://www.ultraheat.com/index.html