I have the Tower Kaos and have to second all the above. Mine had an OS 46FX and it flew great with an APC 12.25X3.75 prop. By now it must have several hundred flights on it. It was so well built(covering being the exception) that I often thought about putting a 61 two-stroke on it and just seeing if it would stay together. And really the only issue I had with the covering was the trim. The basic covering was not really an issue. What better use for all those old servos and unused 72Mhz receivers. I even left the canopy off for that extra speed