Well it's obvious that you don't plan to move that RV any time soon. I have seen a number of RV/Mobile Homes under what we would call a pole barn down here in the south. With a metal roof on the pole barn and several feet of air gap between the bottom of the roof and the roof of the RV.
For a better fix on those gaps you may want to try expanding foam insulation. You can buy it from your local hardware for about 5 bucks a can. Get the expanding type, if it expands into areas you don't want it then slice it off with a knife. I've found a sharp serrated knife does a good job cutting it.
