If you want to go Perfect Fit, I suggest sending the company an email. Their support is really good, and if you find that a piece doesn't fit, they will replace it free of charge. I have sent them videos of my dogs wearing their harnesses to get their help. It's a great harness; the reason most of us go for the mesh ones first is that the PF is expensive and will have to be replaced as your pup grows. They have a fair amount of adjustment, but it won't do from puppyhood all the way to adulthood, unfortunately!
My two adult working line dogs, who are quite slight (26kg), are in M-S-L harnesses.
Pop on over the the puppy section and share stories of Betty - we have a couple of other forum pups at the moment, and several teens, so there is plenty of support. We're a small group, but very friendly. And we LOVE puppy pictures. Just saying
