Tail offset. Think of it this way. Look at a long train from the top as it goes around the curve. The engine in front makes an angle to the caboose in the back. Thighter turn, more angle. It has to do this or you get increased drag.
This is what your plane is doing, think of the wing as the engine, the tail as the caboose. For minimum drag, each flying surface should be aligned along a radius of the circle the diameter your plane is flying. For typical circles inside a gym, the tail will be offset about a quarter or half an inch from along the line of the motor stick. Since these planes turn left best, the tail boom, and tail, should be offset to the left as you look at the plane from the top. Looking from front that will be to the right, from the rear, the left of course.