They put tandem axles on our trailers for a reason. I level using both wheels. You wouldn't take one tire off and run it down the road, would you? If you only use one wheel you double the load on that tire and the 'torque flex' axle.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.