My machine has a walking foot built in so I've been using one for more than ten years and never thought about whether or not the stitch length should be different just because of the walking foot. Why should it be? I adjust stitch length depending on what I'm doing; a longer length when quilting and a shorter length when paper piecing. Sometimes I adjust because of the thread, but never thought of the walking foot making a difference. I'm interested in hearing from the experts on this!