I also read that 4 strokes are better for 3-D, but when swapping engine in my harrier 46 from a 91 Fs to a 91 twostroke my ability to hover really steady and calm, improved 100% over the night, go figure?? Now I have only twostrokes in my 3-D planes exept my new Harrier 100 that has a 180 Fs mounted, but I have not maidened it yet