Thanks everyone..and to OwnedbyJezebel, I think "Yorkzilla" is an appropriate nickname
It's quite clear that no two puppies in any one litter are going to be the exact size, no matter what size the sire and dam are. Of course this doesn't give me or anyone, for that matter, any clear-cut ideas of future weight, but then nothing is guaranteed anyway. We will just wait it out and see. Thanks everyone for your replies