My 4-mo. old Shiloh Shepherd love to pull on her leash when I walk her. I recently purchased an Easy-Walk harness, but I'm having a lot of difficulty fitting it to her properly. The directions show a comatose puppy standing perfectly still for a perfect fit. My puppy rolls over, bites on the straps, and makes it impossible to even try for a good fit...even with treats and praise. Any suggestions other than sticking to her flat collar and leash?