I will stick with u two strokes r the way to go. I have had an os and saito 4-strokes. im not saying one is better than the other but that they deliver power much differently. And u most always will have way more power with two strokes than 4s. Look at hardcore motocross racing. honda's crf450r races in the 250 class. thats 200ccs more displacement to even be competitive with a 2stroke. The guys engineering theses powerplants r some of the best in the world. They simply cant create a competitive 4stoke in even close displacement to a 2. The 2s r always lighter and more powerful than the 4s. I think the guy talking earlier about hardcore 3d is probably correct. I believe that 4 stokjes r a more refined smoother powerplant. If u get low and slow with a 4 u better be a good pilot. when i fly a 4stroker i feel like i have a little lag time in throttle response, meaning i have to be 1/2 step ahead of the plane all the time. With a 2 i feel instantaneous throttle response. Again i think im saying better piloting skill is required for a 4, not a bad thing just different</p>