If it were that easy to breed a correct turn of stifle I would think we would be seeing fewer chocolate dogs with incorrect stifles and we are not. It is often combined with a fairly stuffy front. There are several Bc dogs that have this issue as well. I have a chocolate out of two lovely brown eyed chocolate parents who has lighter eyes (they are ok but not great). He also has a beautiful front and a rear to match, with correct turn of stifle. Given what is behind him, I would not breed to incorrect structure (all my dogs work) to keep a trait that is largely cosmetic. I really don't like light eyes but cannot live with poor structure.

How about 'too much' front? I have seen some dogs who look like they are going to tip forward there is so much chest.

I would call that a prodigious front and complete lack of balance. It's another peeve of mine, I see many unbalanced dogs put up, the judge acting as it they didn't notice too much on one end or the other.

Many times those large fronts are plain fat! It's difficult to if at all able to find the prosternum beneath the extra fat tissue. The same goes for no front but a great or overdone rear. All Labs should be balanced, to some degree at the very least. JMO.