My son and I have similar trailers and use similar tow vehicles but our miles per gallon are vastly different. I think this indicates the importance of trailer frontal area.
I tow with a Honda CRV; he tows with a Honda Element. Identical engines and transmissions.
My trailer is 7 wide x 7.5 feet tall; his is 8 wide and 8 tall. My frontal area is 52.5 square feet and his is 64 square feet. His rig has a frontal area 23% greater than mine.
My tow mileage is 20 mpg and his is 15.5 mpg. His mileage is 22% less than mine.
23% greater frontal area 22% less mileage.
Obviously not ment to be scientific statements but rather to give a feel for the affect of frontal area on mileage.
Norm and Ginny Milliard
1982 Sunline 15.5 SB
2004 Honda CRV 4 cyl, manual