I increase my zigzag width to 6.5mm and stitch length to 2. Do a test piece to make sure your stitches are not to far apart (causing batting to stretch) or to close (causing batting to pucker).
I don't recommend using lots of little pieces of batting for large bed quilts - however great for those smaller projects (i.e. wall hangings).
Batting butted each side of the foot guide.
Small pieces of batting zigzagged together using the ditch foot. There is no loft in the joins - they lay flat.
Do make sure you are joining similar weight and loft pieces of batting .