You could try vortex generators to help improve aerodynamics. I used them on my big Class A motor home, but it gets such low mpg that an improvement might be fractions of a mpg. The ones I used were from a company called Airtab.
Towing on a trailer means one more thing that you have to deal with at campgrounds that are making smaller sites. Some places you have to park the trailer in the overflow about a mile out. Flat tow means you only have a towbar to hook to the vehicle and off you go. Trailers are quite a bit more...