Hi .... Kiki has a Puppia harness too in a size Small. I bought it for her when she was around 5 pounds and it I was able to adjust the strap nicely around her chest. Now she is a little over 6 pounds and she still wears the same harness. I just adjust the strap depending on if she has clothes on or not. There is plenty of room for adjusting.
Anna
www.dogster.com/dogs/511397