Tom, you have to make sure the plane is centered in each loop. If it is centered off the dowel will be off. Also, I can't tell from the picture if you are using 2 lines or one line for the loops. I just use the one line. If using two lines I believe the loops have to be equal in size. Can't really recall on that.

I believe I see a problem in your set up but not too clear from the picture. The loops going around the dowels must be in the same direction on each side. I believe you may have it opposite on each side. I set up my plane with the rear loop first. Then I form my dowel 3-4 loops going in the same direction and then do the front aircraft loop. So the inside of the dowel loops go to the rear and the outside loops go to the front.

See post 12 and 13 and see the loops around the dowel. That is pictured wrong and may be the way you have it. I think. Anyway hope this helps.