.I hear a lot of good things about running 19.5 wheels and commercial tires for fuel mileage and long wear.Would that work for you?I know they have some commercial offroad tires for 19.5 wheels.I'm just not sure they would have the flex or traction without running them nearly flat for traction.
There was a thread on http://www.dieselbombers.com/ about their longevity and better fuel mileage.
Happen to have a direct link to the article?