the contender is a classic.back in its heyday it it flew with a 60 but if you look at a modern day sixty now its much more powerful for the same displacement. you easily fly an os 55 ax and it would be good power.I am getting to be an old fart though and had bought one to use with my 52 fourstroke. but I am not even sure I will build it.I was going with a military scheme so that it looked like one from the vietnam era.plus I was going to change the nose to make it streamline and set the motor at 45 degrees.whichever way you decide its fun fun plane.