I was thumbing thru Overdrive magazine, a monthly mag that's dedicated to the trucking industry and they had an ad for 'Trailer tail'. it's a fiberglass extension that's sorta clamshell shaped that tapers toward the center of the rear gate. The advertiser states it'll increase fuel economy by 1-2 mpg's. That might not seem a lot but when you drive 100,000 miles annually it's a big $$ savings.
2010 Cedar Creek 5th Wheel 34SATS "The Beast"
2006 Ford F350 Lariat 6.0L Diesel
2003 Harley Heritage Softail "Hogzilla"
1988 Harley Softail Custom "The Fireman"
1986 Marriage to "Wifey" (patience of a saint)