Because I'm new here and don't have a Hav yet .....
what is considered average size / weight for say an 8 -10 week old Hav puppy?
What size and weight is considered average for an adult Hav?
I'd be shooting for parents in the 10-12 lb size range. I'm not sure on puppy sizes at that age... Kodi was 11 weeks when I brought him home, and he was a BIG puppy, at 6 lbs. (he grew into a big Hav... 16.5 lbs enen though his parents were both under 12 lbs!
) I THINK I've heard a lot of people mention that their pups are in the 3-4 lb range when they bring them home. Remember that they grow FAST at that age. I also think the most important thing is not to pick a puppy who is significantly smaller than his litter mates. It's not the size SPECIFICALLY that is a problem... It's that a liver shunt can keep them from growing well. So if there is a significant size difference in a single pup in a litter, it COULD be a sign of a problem.
Another way to to check for liver function is a bile acid test, which many breeders run routinely. That does NOT mean for sure that they don't have a liver shunt, but makes it much less likely. Very occasionally, a puppy will develop normally, and only show symptioms of a liver shunt in late puppyhood. That's pretty uncommon, though.
There is always a chance of something going wrong with any living animal, no matter how carefully bred and raised. The best way to increase your odds of a healthy puppy is to buy from a reputable breeder who does all proper health testing. Honestly, there are genetic problems that are much more common in Havs than liver shunts. I wouldn't have that as a major concern if you are getting your pup from a good breeder.