If you want the stripes to run the same direction, you need to lengthen pattern piece "A". Just cut it in half and lay on your fabric with the spread you need to make a long runner. You could also make another "A" pattern piece that is the length you want using tissue paper or freezer paper so that you keep the end angles correct. At least that is what I would do. You do not need any additional "B" OR "B-r" pieces.