Ya, and OT and I are old dogs; but we learned a new trick. Moderate and maternal is the name of the game!
Here is a picture I took of a random commercial cow, grazing in August.
Please take a look at her bag. This was taken because she was where I could get a nice shot. There was no other reason, but it sure shows what I consider a good bag. It maybe could be attached a little further up her belly...
Horseless, you have brought up another point that I have discussed with breeders many times. Angus is a MATERNAL breed and as so, they don't have big butts. I remember Kit Pharo mentioning that when men sat in church pews, they touched and the shoulder, but women touched at the hips. I'm using this merely as an illustration. Limousin, Charolais, etc. have big butts, but they are a PATERNAL breed. It wasn't that long ago that they were used as draft animals and for meat. Not for reproduction or milking ability. So, why the big fuss over an Angus bull having a big butt. You are taking away the maternal when you select for that.
IMHO.
You mentiioned 2100 as did I. When we used him and sons of his,
we got some bad bags. Remember Pine Drive Big Sky? He was a hot
bull for a few years. Until...he had a lot of daughters in production. Suddenly, almost every breeder that had daughters, got rid of them.
Why? Udder quality.
Another thing about 2100; some of them had disposition problems.
And he could be a bit on the hard calving side. However, I see bulls touted as heifer bulls that carry his bloodline. Would I use a bull for a heifer bull that carried his genes? NOPE. Cause it's like the spaghetti sauce, IT'S IN THERE.
I would suggest, like someone else mentioned, go look at the cowherd.
Calving time would be best. Then you can see how the herd is udder-wise as a whole. I've found checking out the cows is a pretty good deal.
I respect you for having questions and not just breeding to get a cow bred, but to get her bred RIGHT.