So, I am going to state what I know, and correct me if I am wrong, and feel free to add more facts.
The heels should be level with the frog as far as height.
The bars should be close to level with the sole.
The wall should be close to level with the sole, also.
The length of the crevice between the heel and the base of the frog extended to the point of the frog, should equal the length from the tip of the frog to the toe.
Also, The process of bringing back underrun heels? I have a farrier coming, but I would like to know what he's doing, and just have the knowledge:)