I have added reflectix above and inside my cabinets above the sink and also in the closet. You can push it into the cavities from there. I also glued it along the headliner area and then covered it with a grasscloth material (instead of the carpet). In all honesty, it hasn't reeally helped much. Unless you can install it in an unbroken film, the cold air will work its way around it. Its just the nature of things. Same way as if you don't have your attic fully insulated, the cold just works its way through any cracks. My heater can keep the trailer warm, but it does not maintain the heat as well as my girlfriend's Scamp
does (which has the insulation / ratfur combo glued all over the inside walls). Would be nice if there was a way to get a foam insulation in there, but too much chance of blowing the hulls apart when it expands.