weights are so hard to guess, so much can creep up from the grand parents or the great grand parents on both the dam/sire side.
I have a litter right now Hattie is 5.5lbs bred to Benz 3.10lbs at almost 12 weeks the kids are 32-36 oz with one exception that looked nothing like his brothers and sister (but did as a baby) "aggie" left this monday for his forever home
weighing in a whopping 54 oz. I know Hatties pedigree well but this was a first breeding to Benz (benz mom "ashlee" is 5.75lbs and his daddy was 3.5lbs and Benz sister under 3lbs) Who would have ever figured a possible 7lbs or larger little boy out of this breeding only time told the story. As he developed I began to notice his differences at about 5 weeks, his weight gain sped way beyond the others.
the end to this story in as much as breeders would like to be right something crops in and throws us for a loop, this gal waited almost 6-7 months for a Benz baby. Becca ultimately didnt mind "Aggies" size but I am sure deep down she was disappointed that at 11 weeks he was almost the weight of his daddy, she loves him no matter his size.
hope this helps