Just keep an eye on him, he'll show you if he isn't getting enough milk. I really don't think size of bag has a lot to do with milking ability. I'll qualify that by saying that some bags, the best kind actually, are attached further up. Also, some cows give richer milk--and don't need a big bag for the calf to do well. There is a lot of factors that indicate milking ability, but the calf is the best indication. Good luck!