Yes, Easytiger, is seeing the picture well. Believe me you will really struggle to hit 300; hope you can do it but you need to be on far less than 50% throttle, all of the rest will be needed to get anywhere near the magic M0.5

By the way, doing it at altitude will not help due to the drop off in engine performance. Fullsize engines are designed to be most efficient at altitude whereas the simple design of our microturbines has the opposite effect.

Rob.