By chin-up, you mean palms facing towards your body right? Good stuff Chubs.
Here is an exerpt of the article I was talking about:
"People used to think that Jarmo Virtanen was just very talented and had good leverages. They couldn't be more wrong. He had many things on perfecting the technique. Once he demonstrated the difference between relaxed and flexed shoulders. By dropping shoulders and using sumo, the distance was 12 inches shorter than using conventional with flexed upper body. He stressed the importance of being relaxed while deadlifting ."
"He stressed the importance of being relaxed, specially in the upper body area and felt it was crucial for getting better leverages in the deadlift and squat too."