Thanks for these replies. It'll be quilted on a domestic sewing machine. I was taught to go for 3 pieces rather than 2, and to avoid a centre seam- I was just wondering if that's what other people do. I like the idea of making the seam allowance bigger than usual. I tend to think that off-centre seams are a bit less noticeable than having one down the middle of the quilt. For a while I tried to use the 108in wide fabric for backings, but it can be hard to find in the UK and the range is so limited. This quilt isn't a precious one, and using stash fabric is the priority.