I have the photoflex medium sized softbox and have used it with nikon sb-600 speedlight. I usually have the softbox just out of the pic frame as close to the subject as possible. I will usually use the speedlight diffuser cap and the softbox baffles, outer and inner.
Here is a pic of a friend and her dog. Used sb-600 in medium softbox. I think the softbox was about 3-4ft away from subject camera right. Both baffles used, no diffuser cap on sb-600
