IMO a gritty bay dog often turns out to be a straight catch dog in a pen when they figure out the game. I've got some dogs that will bay beautifully in the woods but you put them in a pen and I'm lucky if I get to here one or two barks before they catch out.
Thats a good point i have seen that happen as well with korys woods dogs....and I agree that it cant be taught, they either figure it out or they dont,
BUT i have seen the teaching process sped up by using the right bad a$$ hogs in a pen to make a dog bay, same as i have seen a cd's confidence built by starting them on pigs they can handle. With this said i do not do much pen work, but have seen it on a few of my dogs and used to watch some bay pen guys teach there dogs not to catch out, they are pretty smart animials!