I believe you want your Command (I've looked into when swapping engines on a machine) to run with NO load at around 3800 rpm. That way, when loaded with a deck or heavy load, it will "lug" down to 3600rpm. That being said, I believe I set mine to 3700rpm or so WOT with no load.
And yes, these small air cooled engines are best run at WOT when running a load such as tiller or mowing grass, keeps them cool
