I love this pattern! The girls in my guild are making one for our retiring president right now! We each made a chick with fabric from our own stashes and they're a riot! The extra chicks were put on the back... which is making the hand quilting quite challenging!
When you're making your Flying Geese, are you cutting the pieces carefully and piecing them with an accurate 1/4" seam? Make them a little oversized and then trim them down to the perfect size and for perfect points. If you measure the sides of the quilt, you can then adjust the geese to match that measurement.
I think that if you want to fudge somewhere, the center goose on each side or the corners are where I would do it. NO one says you gotta do this quilt exactly as the picture, it's your quilt.