Ive spent the last 30 yrs with 5 roof top heat and air units on the foof of the bus and i dont want to use them on my 1083 camper build im trying to keep the foof clean exept for solar panels which i can protect with 2 in round rub rails on the roof im hopeing someone on S.S. have used and can recomend some type of floor mounted unit that will work in a 18 ft box? THANKS