How long are you staying in one spot? At those temperatures, I'd highly recommend paying a RV skirting place to make a custom set of panels, and using them. This not just keeps the wind from blowing under your rig, but sets up a dead air space underneath. Make sure to add rodent traps, because they will come to the warm area and set up shop, though.
I'd also see about where prevailing winds in winter come from and consider setting up a windbreak wall upwind of your RV.
Utilities are important as well. Keeping the fresh water and sewage hoses warm is critical.