Don
I remember you adding insulation to some areas including wheel wells. What about adding some to the back of the overhead cabinets, or any storage area with a outside wall. I know my overheads turn into ice boxes when it gets below freezing and the foam wouldn't be seen and only take up a inch of storage.
I'm adding to all of the storage areas plus the wall under the table and in the bunks that we don't use. The walls just radiate cold and any reduction in heat loss will be a blessing. We already insulate the windows and vents.