The O.S. .40 LA or O.S. .46 LA will both work well. The airplane will have plenty of power with either engine. For most training flights, even on the .40 LA, you'll be flying at a much-reduced power setting. That airplane will easily "putt-putt" around the sky at 50%-70% power. Trimmed for level flight at that power setting, you just have to add a few clicks of throttle and the model will gently climb. A few clicks off the throttle and the model will gently descend. Hit the power to full and the model will nose up and climb very nicely, thank you.