Breaking in engines is usually done at full throttle, running rich. Slowly taxiing around would not be possible at those RPMs. Trying to break in an engine at idle will not allow the engine to reach proper operating temperature, and could cause premature wear. There are many threads on this subject in the engines forum.

If you don't want to remove the engine from the plane, firmly supporting the plane will be necessary for proper engine break in.

Like FLYBOY said, just don't want to see you ruin your nice plane (or new engine).

(JMHO)