maybe a cheaper fix is to paint [slop] that white insulating roof paint on that is used on mobile homes...I did that to a steel horse trailer....it made all the difference.
2008 F250 6.4 diesel with 50 gal aux tank towing a 2015 Rockwood 2109s Minilite.
2015 Miles and nights
2016 miles and nights
feb. 380/7......march 540/3