I have a saito 125 four stroke on my funtana, I had a ax120 on it at one time but found that in slow nose up flight like knife edge circuits ALL the 2 stroke engines even with a perry pump would tend to overheat and stumble on throttle up to pull out of the low slow knife edge, not a good thing! I considered putting a gas engine in the funtana but did not like the increase in weight that the gas engine, ignition and batteries would add to it. Adding weight to the nose of the funtana would take some of the fun out of the funtana in my opinion! I bought a saito 125 and have never looked back, it is light and has never stumbled on a pull out from hover or a slow knife edge. On heavier planes, 50cc and up, the reliability of a gas engine is more important because they will not float very long when the engine dies, the funtana will float much longer on a dead stick like most smaller planes will.