A rather pointless question it has to be said, but one that has been intriguing us. Does your dog cock it's head when it sees something that interests it?!
DPup was a "Staffie x" though looked almost pure. Now she's about 6 months there is definite signs of whippet as well- too slight, very close coat, tippy toes, very pronounced tuck-up and she is fast :o
One overriding characteristic is the head tilt. It's a quizzical, questioning sort of action and is a very common habit for her. I know of several border terriers who do this but haven't got enough experience of Staffies or whippets to know if it's one of their "things" too :)