I have found that setting the idle is a balancing act that may require you to adjust the position of the throttle servo horn (by pulling it off and replacing it at a different angle on the splines), the linkage clamps (with the set screws), the transmitter throttle adjustment, the carb's idle screw, and the brakes (since they are all interconnected). I would set the transmitter to the neutral trim adjustment, and then adjust the carb's idle screw so the engine will idle, and when you put on the brakes, the throttle linkage doesn't push the carb's slider closed (I'm not sure if it is called a slider, but it is the "butterfly" on the other type of carb mechanism). It is hard to explain, but once it is set, it should just require minimal tweaking every now and then. One change I made that helped me with this adjustment was to put a return spring on the carb (connects the slider lever to a fixed point on the other side of the carb) and remove the spring assembly on the back side of the throttle servo horn. This somewhat isolated the brakes from the throttle. I can post a pic if you think it would help. BTW, 20% is a good everyday fuel.