Right, well thanks for this... but if we strip back a) the economy, b) the noise c) the cost d) prop size e) all 'on' and 'off' pipe problems e) all cosmetic attributes.. and get down to an installation into an AA or freestyle model you think 4stroke is best? More power? I don't think so. Less weight? Nope. More torque? REALLY? When you put the SAME plane with the SAME set up with TWO power plants.. say the YS110 and the OS91.. who will hazard a guess as to the best performance?