I don't know if this is relevant here, but I'm going to mention it anyway, because someone might find themselves in the same position.
At Humphrey's first check up with our vet, he told me he was a bit on the chubby side, and two other people said the same thing, during that week. I got totally obsessed with his weight, spent hours on the net, started weighing his kibble to the last mlligram, doing the same with treats etc.The breeder told me to calm down, feed him (obviously within reason) what he needed and that once he was tearing around, he'd be fine. A fews weeks later, he caught a stomach bug and to be honest I was quite glad he'd got a bit of reserve, as he hardly kept anything down for a few days. He's now 7 months and just over 10 Kgs. I still weigh his kibble, just to have a bit of control but I do feel that "puppy fat" is called that, because that's precicely what it is and I think its a shame that I chewed myself up unnecessarily for weeks. Just wanted to warn any other puppy moms and dads out there, - unfortunately I hadn't found this site at that time, no doubt the advice would have been better!