Three rails it is

I appreciate everyone's advice for setting these blocks. (I am waiting for two more to come from this swap.  I don't know which block will be pieced into the back if I stay with a 16-block layout.)

A pattern called "Simple Stars" in Time-Crunch Quilts by Nancy Martin inspired this setting. I looked it up and was reminded that she set the blocks so that one color was horizontal and the other vertical.  It's more effective than alternating the color direction.  Nancy's quilt is bordered with three strips on each side with the same color placement.  I may copy that...or I may not.