My Reggie is not pure Yorkie (he is 3/4 Yorkie and 1/4 Lhasa Apso) but he weighs 10 lbs and will be 1 year old on Aug 11. He is bigger than a yorkie but smaller than my friend's silkies. To me he is the perfect size for him! LOL! I have seen larger pure yorkies around here too. In fact my daughter's best freind's yorkie is a bit on the larger size because she is around 4 lbs and about the same age as yours.
Here she is with Reggie:
http://i4.photobucket.com/albums/y10...metovisit1.jpg http://i4.photobucket.com/albums/y10...metovisit4.jpg