There's nothing wrong with trying to improve current MPG. Of course towing and MPG are polar opposites.
Consider this: If you get 10mpg, and manage a 1 mpg improvement, you just increased your MPG by 10%. At $2.00/gallon you just saved yourself $10 over 500 miles.
Oh, and one other thing - a saying on the ecomodder forum I linked earlier "the single biggest improvement to mpg is to fix the loose nut behind the wheel". In other words, learn how to maximize what you have with your driving style.
I have personally picked up 1.5mpg by simply changing my driving habits while towing. And this is verified on a route I regularly take to our favorite campground. Improvements can be obtained. Just a matter of whether it is worth your time or money to do so.
Gas at $2.00/gallon? May not be worth the work. Gas at $5.00/gallon? May well be worth it.
It's all relative. YMMV. :D