i would just add the rows needed, clip then wash- that would be easier than (ragging) first then attaching- i've enlarged lots of raggy quilts- make them throws to cuddle with then person wants them queen sized instead...i just add more rows, clip & wash- easiest quilt i know of to enlarge after being finished...since i tend to clip (rag) the outside around the quilt i generally use painters tape & tape a straight edge around the quilt holding all the frayed edges together- then add the new rows, using the tape as a seam guide- then remove the tape- clip the new seam allowance- sew all the way around again & clip- then into the washer/dryer.