If you can find a OS 91FX, it is even lighter than the OS 61FX or the 75 AX and has more power. You'll have fantastic climb rate. Keep throttle management in mind in level flight or dives, listen for flutter, that will kill a plane if you don't back down instantly. The OS 91FX with a plastic needle valve is the most trouble free of that model and less expensive to find new or used than the new 75 model (great runner too).