Good observation Gene. I think it was primarily a British thing, that Capt. Money got over

Albert William Money, Arthur Corbin Gould, Pigeon Shooting: With instructions for beginners and suggestions for those who participate in the sport of pigeon shooting, 1896
http://books.google.com/books?id=qkEEAAAAYAAJ
In the course of the last twenty-five years, I have met and known intimately most of the best known trap shots. I am one who believes that the longer I live the more I can learn, and that other people's opinions are always worth considering, and perhaps adopting, if, on careful consideration they are found to be based on facts and good judgment.
Stand with the left foot thrown forward, the body upright, and the feet slightly apart; in fact, very much in the attitude of a boxer. The higher the gun is held, the quicker you will get your aim on the bird; therefore, hold it as nearly up to the shoulder as you can, the left hand well extended, but not to its full length, or you will be hampered in shooting a bird coming straight toward you. Take care that there is nothing stiff or rigid about your body, arms, legs or head; grasp the gun very firmly with both hands.

His "ready" position

[Linked Image from photos.smugmug.com]

I believe this is him shooting inanimate targets; an "open" stance with slight bend to the left knee

[Linked Image from photos.smugmug.com]