I did use the larger thicker spring, but I did the opposite of what the directions called for. The directions called for the spring to be closest to the wheel, but I couldn't get it to work out that way. I have the spring located directly below the surface of the rudder, and then bent the small side up into the rudder with ca. I flew it yesterday, but I took off from grass where I usually take off from pavement. I didn't really notice how well the steering authority was.