Generally speaking, if the 8 sections don't match when sewn together - at least one of the sections is the wrong size. If I were you I would measure (down to the 1/16th inch) all four sides of each of the eight star arms and trim (if you can) the ones that are oversized. After that - put it back together as CKcowl suggests. Starch helps too - but remember now that they are pieced ALL the edges are bias edges so don't stretch it when you starch/iron it.