One time I took apart and inserted an entire row of blocks on a quilt that I'd finished but decided it had to be bigger. I only had the quarter inch seam allowance available on the existing blocks. There wasn't too much of a problem about the quilting because each block had a separate circular quilt design that didn't come right up to the edges. I first sewed the new strip of blocks to the old ones on each side by machine, using the standard quarter inch. Then used Marti Michel's iron on batting tape to join the strip of batting. For the back I had to add a wide strip of the backing fabric. I had no seam allowance at all on the original piece of batting because I'd had to cut it all the way down the quilt, so I had to hand sew the new piece, overlapping on both sides. The width of the seams wasn't very important, but of course had to be enough fabric available to allow for any unanticipated miscalculation. It helps that my backing had a busy print. Only an expert quilt judge would be likely to guess what was done. I use the quilt in a guest room, and when I make the bed a few times a year I habitually try to find that newer strip because it theoretically would help me figure out which direction the quilt goes on a queen bed, but it's too hard for me to find now that some years have passed and I don't remember which fabrics were in the new row. Also, on that quilt, the border was piano keys in a wide assortment of colors, so that was easy to add in the same way as the rest of the row. The long, narrow inner border would naturally have an occasional seam, and there are two closer together there, but they're lost in the quilting. Same with extra joins in the binding. Nevertheless, it taught me to decide what I'm doing before I proceed.