Pizza, Four strokes will work great for 3d, becasue of their instant throttle response and they will swing a larger prop (very important for post stall) at a lower speed (larger props swinging slower are more efficient than smaller props spinning faster) and if you get a light four stroke like the ys 63, you will have plenty of unlimited vertical while swinging a larger prop allowing you to have more control authority at low speeds while weighing just ounces more than a comprably powered 2 stroke. 4 strokes work great for 3d. instant throttle response is another important aspect, which not too many two strokes have. fast throttle response is good, but i like the ys engines. they are at full throtle as fast as you can open up the carburator. go with the ys 63 and you will be very happy i assure you, or the saito 82. i have not owned either, but i have opperated them and they are phenominal engines; both of them.