I could care less about any savings in mileage (I still say if you're worried about gas mileage, you'll not have much fun RV'ing, towing sucks up gas).
What the aerodynamics of the Trail Cruiser does for me is allows me to tow a larger heavier trailer with my anemic low compression engined '94 GMC Suburban.
Used to towed a 22' '04 Tahoe Lite (yeah right) with a front profile that was flat at the bottom 18" or so then sloped steeply back to the roof, and had the poorest design feature ever, a flat back. weighed about 5000 loaded. The Trail Cruiser is 26' 11" long, weighs 4800 (certified scale) lightly loaded and is much easier to pull. Probably 5500+ loaded.
When we decided we didn't like the 48" wide double bed, underneath a bunk (hard to get in and out with bad knees, shoulders, etc., and since we had had a 30' Trail Lite a few years ago, we decided that we had to find a certain Trail Lite or Cruiser with a queen bed and couch slide. Took about a year, with 700 mile trips to see junk, finally found one 35 miles away.