I read the AMA rules and they say 70' line length. I was told that at the Nats it is 70' from center of the aircraft to the front of the handle. What is the correct measurement. I am on 66' lines and want 68'- 69'. Thanks in advance. 
Thanks from Curtis Shipp.
The 70' refers to the handle to the center of the airplane. That arose in the other CL events where the radius of the path travelled is important to the performance, like speed. What actual line length you need to get to 70' depends on the airplane and the length of the leadouts.
This generally is not an issue in stunt, since almost everyone is short of the 70' "handle to centerline" measurement for performance reasons anyway. I run 64' lines (actual eyelet-to-eyelet length, not the "speed rules" measurement) and that puts me around 66' 10" measured the other way.
Brett