It's also worth keeping in mind a couple of things.

First, idle reliability improves with run time. I doubt you have enough time on the engine for the idle to have really become as good as it will be.

Second, idle rpm varies with prop diameter. Heavier and longer props have more flywheel effect, allowing the engine to idle lower.

Third, the prop brand, pitch, and diameter will affect how much thrust the engine is producing at idle, which basically is how hard the engine is trying to make the airplane roll.

Fourth, what surface your plane is on, and how friction-free your wheels are will affect how hard the airplane fights back against the engine to keep from rolling.

All that put together means that you might or might not be able to get a plane to stop moving on a smooth paved surface, but most planes will stop moving on grass easily. If your on pavement, you can always add a little friction to the wheels by moving the wheel collars against the wheels a little.

Oh, as for actualy rpm, anything below 2k is pretty good for most new 2-stroke engines in that size, some can get close to 1k, depending on the details.