If you are just setting up one of these, the neutral position for the ailerons will be the centerline of the wing. A straight edge is as good as anything for finding the centerline on the outer end of the wing. Some like to mix a little spoileron or flaperon in just for kicks but it is absolutely not necessary. The CG will be a bigger factor on how she lands. Most end up with the plane trimmed in such a way that she will settle down into a nice three point landing. Happy landings!!