From a long arming perspective it would be better to have your seam run horizontally. The bulk of a vertical seam rolled up on our rollers can be problematic and result in a fold in your backing. That said, we can't guarantee the horizontal seam will be EXACTLY in the center of the quilt. If this is an issue for you then you will want your seam vertical and trust your long arm quilter to do her/his best to keep the backing smooth. Use 1/2" seam allowance and press the seam open to reduce bulk. Be sure you have removed selvage.

This is helpful information that I, as a relative newbie, would not have thought about. This quilt is a large throw that I'm taking to a friend with a bigger machine. Not a LA, but longer than what I've got . I hope it doesn't give her any fits. We both do our best work and I really trust that it will look great, regardless of problems.

What a great title! I'll check it out when I get a chance . Right now I'm under the gun to baste this thing and get 'er delivered to my friend this evening.