Have you found the puppy growth charts to be pretty accurate? One of the "sticky threads" here on the "General Yorkie Discussion Forum" had this link:
http://yorkiepassion.com/growthchart.htm
According to the growth chart here... if Gus is currently 10 weeks old and weighs 2 lbs. 1 oz, he should be 5 pounds when grown. Do you think this is true?