I use a harness on both of my dogs just because I think it is safer. But trust me Ella HATED it when I first started putting it on her. She would growl and even try to bite, but now she has figured out putting on her harness means she is going bye bye so she has been ok. I think it just takes awhile for them to get used to. And seeing your chi is only 8 weeks I really wouldn't worry.