Hello, our little boy (13 weeks today) will be allowed (per vet) to begin going on walks next month. We live in a large urban area and currently take him out in a pup stroller to get him acclimated to the noise, birds, people, squirrels, and other dogs. He is a great joy with a friendly and lively personality and has done very well but I can tell he will be a puller as he is quite active and strains on the stroller cables, standing up for most of the ride. His neck is currently 7 3/4" and girth is approximately 13". I would like to find a harness that can be adjusted as he grows and also one that will be safe and not easy to escape from on city streets. Thank you in advance for any suggestions!