From what I understand they don't stand on their own. You have to make them stand
If you don't they will be floppy which is super cute too!
http://www.yorkietalk.com/forums/3757090-post20.html has a video about taping
Oh and he will keep growing for a bit, I'm sure! I hear that doubling the weight at 12 weeks will give an estimate of their size.
Mine is 6 months and 4 pounds 9 ounces.