Most all of the older generation of tiers (Darbees, Dettes, etc.) recommended having the elbows at your side, with about a 90 degree bend at the elbow to prevent shoulder fatigue. All of these were commercial tiers. This seems to be the arm position of the women shown in the photos of the ladies tying for Dan Bailey in his shop back when. This is the position I have used during my nearly 30 years of tying.