Im in the process of planning my build... Im building on a 2001 fg with a 14ft flatbed.... I decided to use a truck camper and build off of that...Im looking at 2 different truck campers...The first is a lite weight type where the roof cranks up....The second is a a hard side....The hard side will extend past the top of the cab...With diesel prices extremly high mpg is definetly a factor in the build...Im wondering how much the difference in height will effect mpg?