Just thought I'd mention...
I took My Female Becca to the Vet yesterday for a checkup, and She weighed in at 8.3 lbs ! What a little Fuzwhopper she's going to be.
I sincerely think that a higher level of exercise (which both of mine get daily) has an impact on how much they grow. Both Her and Sneakers parents are within normal specs and Becca (when born) was not an exceptionally large puppy. It may vary with another animal ?