I have a Hog that origanly had an os 91 one it and that combo was perfect buit I eventually needed the 91 for something else and subbed for a 70 os surpase and it still flies fine with it, all off grass. I used a aluminum gear bolted on in front of the wing l.e. and it works great. Just keep the axle at least 1" in front of the L.E.