The rear shape may be better than many realize. Remember, it's a camper. It's not supposed to go 70 mph. 50-60 may be too fast to enjoy the ride. Think blue highways. The speedo may spend a lot of time between 30 and 45. When you slow down air softens, and sticks to sharper final tapers. That body transitions very smoothly. No first derivative discontinuities and second order looks very low. As for stripping creature comforts for a small MPG gain - phooey! Meet the functional requirements of the vehicle and it's intended purpose first. Not getting any sleep suffocating in your own sweat sucks the fun right out of travel.
Cheers
KB