I teach Log Cabin as a beginner quilt class..what I see is.. it's usually in the cutting or 1/4" inch in the sewing..Eleanore Burns way of pre-cutting(long strips) and chain sewing is the safest way to do them..if your chain piecing and a little off.. they all will be a little off..therefore they will still match up!! You should always square up after each round..hope this helps..lol..yes I cursed a lot just lately..working on a Bargello !!