Fox,

I am currently finishing my first kit as well, a 4 * 60, which is practically ready for covering. Upon reading the instructions in the kit on wing mounting, it hits exactly on the point you mentioned, and according to the instructions, it is not uncommon for one one wing-half to be slightly longer than the other wing-half upon completion of construction and joining of both halfs. In the case of the 4 * I am working on, what Sig suggests is marking the center of the Fuse in the front and also rear of the wing cradle. Measure the span of the wing, and mark the center on both the leading and trailing edge. Place wing on fuse, alligning marks on wing with those on fuse. Measure from wing tip to fuse end, if both measurements are same, your good to go. If they are differnt, keep the Leading edge mark alligned, and rotate the trailing edge until both measurements are the same, then remark wing trailing edge center. This should correct your problem. Hope this has helped.