It's a gorgeous quilt! I love log cabins and how many different ways there are to configure the blocks! I usually don't do borders, but when I need to, I tend to do a narrow inner and the outer about 2.5-3x wider that than. Take pictures with your digital camera and see if that helps you get a better feel for size. If it were my quilt, I'd probably end up doing a 2" finished inner and 5" finished outer border.