I know exactly what you are talking about. My harness fastens just above the shoulder blades, very tightly, and I have never had Rusty back out of one. You see the diaper pin can be adjusted so that the harness fits tightly and she can't get loose with a diaper pin adjusted correctly. My harnesses were made of cloth.
Here is a link I made... still haven't been able to post a picture.
http://www.yorkietalk.com/forums/pic...pictureid=5998