My 2 cents- having visited the factory many times (every time I get by Ft. Smith, I make it a point to swing by and get Fox glow plugs) all I can say is take a serious look at the engines. I ran Fox .40s in my pylon planes using Omaga 15%. These were the plain jane bushed 40 -but they were Powerhouses - I was lucky and had ones that always ran well at full throttle. In fact, I sold my last pylon racer with .40 on it a couple of months ago. The engine had not been started in three years, the buyer and I cleaned the carb, put fuel in the tank and started it. A couple of days later, he was flying it at the field and it still hauls butt. As said before, they are not plug and play, but they are reliable engines once broken in correctly.