Put the Moki 1.8 or the 2.1 in it. The O.S. 1.60 FX and the Moki 1.35 are both great engines. I had both the Moki 1.35 and the 1.8 available when I put mine together and went with the 1.35 first. I thought the plane flew fine until a friend showed up with a Moki 2.1 stuffed in his. After letting me fly his plane I went home and put in the 1.8 which made a considerable difference. If I were going to purchase a engine for this airplane it would be the Moki 2.1 and I would never worry about power.