I hate to give away my secret, but the way I do the snapping circle like on the 2002 TOC video or the XFC in 2003 (I think) is actually easy. The do it you need the right airplane. One with 3D rates, and very good horsepower. I have found a lot of smaller models wont do it well, the larger 40%er do.
I enter inverted, on 3D rates. Go to full power, full right aileron, full right rudder, full down. You ther fly the elevator between up and down to keep the nose up and keep it turning through the circle. Its easier than harrier rolls in many ways, because you are only flying the elevator. Rudd, ail and throttle stay buried.
So in reality, the airplane is transitioning between a deep inside snap for 180 degrees rotation and a negative tumble for the other.
Take note of where the nose ends up relative to the horizon, too much elevator or for too long and the nose will rise too high, the speed will drop and the rotation will stop. Some models like nearly equal up and down input, others dont. I first came up with the maneuver with a 40% Carden Edge 540, and it didnt like much if any up elevator input, most of the steering and holding the nose up was done with down elevator.
The Carden Extra 330 and 260 seem more symmetrical on elev input. The H9 Ultimate does it really well, and you can go either same rudder and aileron or opposite rudder and aileron and still steer it around the same with elevator. Some have commented that the Ultimate doesnt look as impressive as the monplanes though, because it stays more axial through the maneuver where the monos get more buried and rotate around all 3 axis more.