A few notes. I am not one that says dogs HAVE to be conformation champions to be bred.. as long as the reasons arent basic structural. Over angulation seems to have more of a soundness issue than under angulation in small dogs. (observation in agility points to less angulation in the rear is better for performance and long term health) A keel shaped chest is bad in JRTs, but has no actual detriment to the dog health wise. It just makes it harder for them to fit down a groundhog hole. However both Snip and Dekka have proven that they, and their non round chests, can and will fit down ground hog holes. A soft coat will put you out of the ribbons but isnt a detriment to the dog.
Things that are bad. Crooked legs, malformed spines (though you can win in conf with that it seems in many breeds) Extreme angulation or underangulation (Twist is borderline under.. if it wasnt for the fact that she was sound as could be at 7 as were all her children I might have passed on her) Temperament issues are VERY bad. No matter how sound a dog is physically it needs to be sound temperamentally!! Lack of bone. I am not a fan of spindly dogs that arent supposed to be spindly. Its too much weight on their articular surfaces.
Basically anythign that will cause the dog to be unsound and/or unsuitable for the work it was bred to do is bad.
On the flip side breeding for a style in the ring that is winning, but precludes the dog doing what it was bred to do is also very bad IMO.. but that is another post.
