Towing an r-pod

I purchased my R Pod 171 3 weeks ago. Overall I am very happy with everything except the mileage I get towing it. Before the Rpod I had a Jayco popup and got 17-18 mpg. Towing nothing I easily get 22 mpg. Due to the specs of the R.Pod, I figured I would get maybe at the worst 15. Actual mileage on 2 trips in areas of some but not a lot of hills was 11-12 mpg. My vehicle is a 2009 Jeep Grand Cherokee with trailer tow package and the 3.7 liter six. I did as the car manual said and auto shifted into 4^th instead of drive to ensure that the overdrive did not try to kick in. The car stayed in 3^rd almost the entire trip, would not shift into 4^th except on dead level pavement with no wind or downhill and my RPMs were 2800 at 55 mph.

The Jeep is rated to pull 3500 pounds on a trailer with a frontal area of 40 sq ft. The R.Pod is well under the 3500 pounds with my added gear and options and according to Forest River the frontal area is between 12 and 25 sq ft. I have read all of the miles per gallon posts on this site and the R.Pod user group site and most six cylinder engines are getting about the same as me. The most interesting posts were the ones that seemed to show through computer simulation that there may be quite a vacuum forming behind the Pod that really hurts performance and mileage.

My questions are as follows:

Has anyone actually used air deflectors or foils on their vehicle or on the R.Pod and if so, did they help performance or mileage?

Has anyone successfully tried any other devices or techniques to improve performance or mileage?

Thanks