Ditter43, I think there are two main reasons for not having a seam running down the quilt. First, since it applies to all quilts, has to do with wear and folding. Second, for a quilt that will be quilted on a longarm, a seam down the middle will roll over and over on itself, causing a ridge and uneven tension on the fabric. A horizontal seam works just fine. My favorite is a diagonal seam, done according to a formula by John Flynn. It often saves fabric and the seam will never roll on itself or be folded on itself.
--Heidi
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