Darren, thanks for the information about contrasting fabrics in the two outside rails. I have been looking at pictures of rail fences, and quite a few have the medium fabric in the middle. That makes what you say make sense too. So in the quilt I am going to make next, if my dark purple and lighter purple don't have a lot of contrast, I will be happier with my white fabric on the outside. Yes....this helps me a lot. Thanks again.
Dina